Three Ideas involved in Selection.

Fig.1.Diagram to illustrate:A, the transmission of acquired characters,B, modification of type by natural selection. InAan individual of rounded proportions, at the top of the diagram, has two children. Environment is represented by a board with holes through which they must pass. In so doing they become thinner, transmit the thinness to their children, and so on. InB, a man of rounded proportions has two sons who vary, one being fat, the other thin. The fat one cannot get through the hole in the board; but the thin one does, has children who again vary, the thin one having an advantage.Three Ideas involved in Selection.Now there are three ideas in this law of natural selection: first, that there are inborn variations among the offspring even of the same family; secondly, that these various individuals living in surrounding conditions on the whole uniform and common to all of them, will start in life, some with an advantage and others with a relative disadvantage, and that those possessing an advantage will, more of them, tend to produce offspring; thirdly, that the variations, inborn in this case and not acquired, will probably be transmitted. That there are marked variations—physical, mental, and moral—among a litter of kittens or puppies is within the experience of everyone who has kept them, and that variations in human families are as marked is known to everyone who has brothers and sisters. Even twins frequently differ considerably from each other, and it is said that the last years of the lives of the Siamese twins were sadly marred by their opposing views as to the rights and wrongs of the American Civil War! It stands to reason also that these variations may be of advantage or disadvantage to their possessors, and that among animals and plants, where there are no social props given to the weak, the variations may and do determine survival. To give an idea of the rigorous operation of selection which we find among the loweranimals, we have only to enumerate the number of the progeny produced by each pair, which is often prodigious, and knowing as we do that the number of individuals in a species remain virtually the same in a given district for long periods of time together, we conclude that the room of the parents is just filled by a younger pair, and all the excess of their progeny over and above this one pair must have succumbed to surrounding want and hardship. To give one concrete example out of hundreds that might be selected, let us take the case of the golden eagle given by Weismann in his essay on the “Duration of Life.” He says: “Let us fix the duration of life in the golden eagle at sixty years, and its period of immaturity (of which the length is not exactly known) at ten years, and let us assume that it lays two eggs a year, then a pair will produce one hundred eggs in fifty years, and of these only two will develop into adult birds, and thus on an average a pair of eagles will only succeed in bringing a pair of young to maturity once in fifty years; and so far from being an exaggeration, this calculation rather under-estimates the proportion of mortality among the young.”But in all probability most of us are more conversant with the ways of the domesticated cat than with those of the golden eagle. The cat produces its first litter of three or four before it is a year old. Itskitten-producing life lasts, say, for eight years, and it may, on a low estimate, be supposed to produce a litter of four kittens once in each year. In all a cat will have, on a fair estimate, thirty-two kittens, and may be a great-great-great-great-great-great-grandmother in her lifetime, yet we do not observe in town or village such an alarming increase in the cats from year to year. Their number is pretty stationary, kept so by the enormous destruction of their progeny. The enormous capacity for reproduction of a race of animals, where for a time their surroundings are favourable, will be appreciated by the lowland farmers whose fields were laid waste a few years ago by armies of short-tailed field-mice, whose natural enemies, the hawks, the cats, and the weasels, had been extensively shot or trapped.The struggle to survive among the savage tribes of man must be excessive. Whole races come and go, and their survivors again fall victims to privations, disease, or natural enemies, before the white man with his better brain and capacity for adaptation.Selection is a Fact, not a Theory.The third idea in the law of natural selection—namely, that inborn variations are transmitted—is also a fact that is universally admitted not only among biologists at the present day, but by thosewho trust only to their everyday experience. “The child has its father’s temper,” or “its mother’s eyes,” are expressions heard in every nursery, while the innumerable cases of the transmission of inborn drooping eyelids and supernumerary fingers and toes show the same thing in a more striking manner.The law of selection is therefore no mere unproved fancy, it is a statement of fact, and of one which is so obviously true that it is now almost universally admitted, not only among specialists, but by most intelligent and educated persons. It was understood, and its significance partly appreciated by Malthus, and I find that even he acknowledges a prior claim ofFranklin’s.[2]Romanes[3]tells us that the idea occurred in 1813 toDr.Wells, and in 1831 toMr.Patrick Matthew, and the wonder is that other thinkers have passed unnoticed such an obvious phenomenon.How much is explainable by Selection?While, however, natural selection as an agent capable of producing racial change is accepted by almost every well-instructed biologist, there are some who are still inclined to give some value to the operation of the Lamarckian transmission of acquiredcharacters. They do not deny that to selection is due by far the most obvious racial changes, and that experimentally the most potent factor in the production of a new variety of a plant or animal is selection. They are, however, inclined to believe that along with this, there may be some transmission of acquired character, only discernible after the lapse of many generations. Darwin himself thought that this was the case; he held that certain racial distinctions were due to the action of the environment on the parents and the transmission of the change thus produced upon their offspring. In his great work upon “The Variation of Animals and Plants underDomestication,”[4]he enumerates some of these. They may be divided roughly into two classes: first, instincts and habits; and, secondly, results of use and disuse. Darwin believed that the trained habits of dogs and horses, the tameness of the rabbit and other domestic animals, were due to the direct and transmitted effects of man’s contact. He held that the large size of the leg and small size of the wing of the domestic as compared with the wild duck are gradually acquired and transmitted by use and disuse.But Darwin, as Huxley pointsout,[5]was inclined to lay less stress upon the transmission of acquiredcharacters in his later writings; and we find that in the “Origin of Species” he is inclined to abandon them altogether, and accept the position now held by the Neo-Darwinian School of Galton and Weismann. He says (pp.117, 118), “If under changed conditions of life, a structure, before useful, becomes less useful, its diminution will be favoured, for it will profit the individual not to have its nourishment wasted in building up useless structures.... Thus, I believe, natural selection will tend in the long run to reduce any part of the organism as soon as it becomes through changed habits superfluous.”Just as Darwin himself, as time went on, laid more and more stress upon the importance of selection, and less and less upon the transmission of acquired characters, most naturalists have tended to follow him in the same direction. It may be said, I think, without gainsay, that, since Darwin’s death, the most important and outstanding work done by the biologists has been the uprooting of much of the Lamarckian doctrine, originally held, not without question, however, by Darwin himself. The biologist of to-day is more Darwinian than Darwin, and explains on the Darwinian hypothesis even those cases which had presented difficulties to Darwin’s own mind.Galton and Weismann.Amongst those who were pioneers are Galton and Weismann, and, curiously enough, in England and Germany these two men, independently of each other, came to the same conclusion respecting the non-inheritance of acquired qualities, and pointed out that the facts of development indicate that the generative matter is passed on from one generation to another, remaining intact in the body of the parent, and that we have no reason to suppose that it could be influenced by changes in other parts of the parental organism. It is not uninteresting to note and contrast in these two investigators the action of the typically English and typically German mind, more especially as the comparison is perhaps equally complimentary to the two nationalities, and indicates the value of results arrived at by workers of different individualities.Galton was first in the field, and as long ago as1876[6]made the following clear and concise statement:—“The conclusion to be drawn from the foregoing arguments is that we might almost reserve our belief that the structural cells can react on the sexual elements at all, and we may be confident that at most they do so in a very faint degree: in other words,that acquired modifications are barely, if at all, inherited in the correct sense of the term.” Thirteen yearslater[7]he expresses himself in practically the same terms. An untiring investigator, chiefly in the facts of human heredity, he briefly sums up as above one of his most important general conclusions. It is all he has to say, it is all that his facts permit himto say.In 1882, Weismann[8]questioned whether there is as yet any proof that acquired characters are transmitted; he writes:—“The theoretical conception of variation as a reaction of the organism to external influences has also not yet been experimentally shown to be correct. Our experiments are still too coarse, as compared with the fine distinctions which separate one individual from another, and the difficulty of obtaining clear results is greatly increased by the circumstance that a portion of the individual difference always depends upon heredity, so that it is frequently not only difficult, but absolutely impossible, to separate those which are inherited from those which are acquired.”Since that time, Weismann, in a series of importantessays,[9]indicating a profound knowledge not only ofcomparative morphology, but of the habits and modes of life of a vast number of animals and plants, has shown that many of the cases which Darwin was doubtful about may reasonably be explained by selection, and he has marshalled a vast mass of evidence in support of the argument that acquired characters, experimentally produced, are not transmitted.These essays are profoundly interesting, and will supply food for thought for many years, but it must be admitted that Weismann has gradually been led away to speculations of the most elaborate kind, built upon the most flimsy substratum of fact. There is evidence of this tendency even in his early writings, but in his later essays, especially his recent work on “The Germ Plasm: a Theory ofHeredity,”[10]the speculative part quite overpowers the rest.As those who are interested in heredity will probably read his works with the greatest attention, I have ventured in anappendixto make clear what in his works may, in my opinion, safely be looked upon as speculative rather than legitimate, or even provisional, generalisation, and what, therefore, may be altogether omitted from the study of a practical problem such as that with which we are concerned.Are Acquired Characters transmitted?The practical issues which both Galton and Weismann have raised cannot, however, be underestimated, and, in respect to the non-inheritance of acquired characters, the mass of modern thinkers may already be said to have given their allegiance to the views of those two thinkers.But we are living in times when mere authority is at a discount, and we may well demand the facts for ourselves. The point which we are inclined to question is one as to which a doubt was often present in Darwin’s mind. Granted that selection is a factor, we are inclined to believe that the transmission of acquired characters must also take place, at any rate, to some extent. In attempting to decide this question upon the facts themselves we may take two lines of research. In the first place, we may examine every case of racial change, the production of new or different parts, the development of a new instinct, or the degeneration or loss of parts or instincts present at some past epoch. If in every case we are not compelled to exclude natural selection, and if in every case that we can directly and experimentally follow, selection is the outstanding factor, then there is strong presumptive evidence that racial change is caused by selection and not by the inheritance of acquired characters. In the second place, we mayartificially induce the acquisition of some character, and notice whether this is transmitted; if it is not, then the general operation of this kind of transmission is rendered very doubtful.Many Cases of Supposed Transmission to be explained by Selection.It is upon these two lines that Galton and Weismann worked, and we may now follow in rough outline the evidence they adduced. Darwin had been able to explain, to universal satisfaction, the evolution of many types and varieties, as a result of selection alone; though certain cases of the supposed inheritance of use and disuse, and of acquired instincts, caused at times doubts to arise in his mind. But Weismann has questioned this inheritance, and has shown that—as Darwin himself sometimes believed—these may readily be explained by selection alone. The gradual increase, generation after generation, in the size of a useful limb or the perfection of a valuable organ of sense may readily be explained by selection. The fact that the limb or organ is of use to the race in its struggle will determine the survival of those born with these serviceable parts well-formed, and these in their turn will produce others as favourably or more favourably constituted, from whom further selection can take place. We cannot shut our eyes to theoperation of selection in such instances, nor have we any reason for saying that part of the effect must be due to some other cause. In the case of organs which become useless and finally disappear in the course of generations, a selective agency will sufficiently account for this disappearance. As Darwin himself pointed out, a useless organ is an expense and a drain upon an animal’s capital; it requires blood, and its exercise uses up some of the sum total of energy the animal possesses. The truth of this can be shown experimentally, as when compensatory growth occurs in the rest of the body after amputation of a limb, or when one lung or kidney enlarges subsequently to the disease or removal of the other. In cases where an organ is useless, those who have it badly developed, and in consequence have other and useful parts more fully formed, will have a distinct advantage over those born with a well-formed but useless organ. We may thus explain the small size of the wings of the tame as compared with the wild duck, an instance in which Darwin saw difficulty in excluding inherited disuse. In this way we may explain the occurrence of the still smaller wings of the running ostrich and apteryx; also the blind fish of the Kentucky Cave, and the visionless eyes of the burrowing mole. As an illustration, an animal or man may, in this respect, be compared to an individual with a given amount of capital, who,if he spends his money in one direction, will thereby have less for another purpose. In this way a big leg may be obtained at the expense of a small arm, or a good ear be the cause of anindifferent eye.When we turn to the question of the supposed transmission of acquired instincts and habits, we find that it is possible by means of the principle of selection, to explain some, at least, of the cases which presented difficulties to Darwin’s mind. Thus the tameness of rabbits, cats, and dogs, which animals have for countless generations been subjected to domestication, need not necessarily be accounted for by supposing that the results of training are transmitted. For it is easy to understand how those that would have rebelled most against man’s authority, and who were by nature the least tractable, would have been less cared for by man, and probably would finally have suffered extermination, while the docile received his attention, and were allowed to reach maturity and perpetuate the race. That this selection must be going on at the present time is very obvious, and as instances we may note the savage dogs that are constantly being destroyed, and the house dogs and domestic pets that are, in most cases, continually being selected from the docile animals and those of good temper. A dog that does not possess these good qualities can have no existence in town or village, and so by continualextermination of the unfriendly, the “friend of man” has gradually been evolved.Paucity of Experimental Evidence of such Transmission.Turning now to those cases in which characters can be acquired or experimentally stamped upon an individual, we find that no single reliable instance can be adduced in which transmission takes place. Mutilations have been practised upon male infants by Jews and other Semitic races for thousands of years; yet, in spite of this, the operation has still to be performed, for the lost parts appear in the offspring of to-day as in the earlier periods of their race’s history. Certain breeds of dogs and sheep have for many generations been systematically docked, and yet the young are born with as long tails as those of other breeds. Chinese women have compressed their feet from times long past in their history, yet Chinese female infants are still born with large feet, and have to undergo afresh the torture of their compression. More curious still, for it affects an organ of paramount importance, the brain, there is a tribe of Indians who flatten their heads in early life, entirely changing the shape not only of the skull, but of the brain itself, yet their children are born with normal rounded heads; the induced change is not transmitted.It must be admitted that this evidence is pretty strong, and we need not wonder that it has produced such widespread conviction, although it has been so lately taken up by the thinking public.The Reproductive and the Body Cells.The body of a plant or animal is composed of small living bodies, most of them of microscopic size, called cells. These lead, to a certain extent, individual lives, and have individual characters, but they are built, as it were, together, like the bricks and stones of a house, to form the body. The cells are, all of them, nourished by the blood and lymph, and some are connected together by strands of connecting matter termed nerves. All the cells of the body are descendants from a single fertilised egg, which has resulted from the fusion of a paternal and maternal sexual cell. Among the cells of the body, and situated in special organs, are the sexual cells, likewise nourished by blood, but not connected by nerves with other parts of the body.Reproductive Cells unaffected by Local Changes in the Body Cells.Now there is no reason to suppose that these sexual cells residing in the bodies of the parent willbe influenced by a change in the muscle or brain cells of the parent unless this change in some way or another influences the blood, the common go-between. But the blood is now known to be but a food and oxygen carrier, and an eliminator of used-up products. It is like a river laden with vessels carrying corn for the food of the big city, and nothing more. The life, the energy, the character of the body is the sum of the lives, the energies, and the characters of the cells—although these necessarily require the nourishment derived from healthy blood—just as the life of the city is the sum of the life of its citizens who require the nourishment of the corn.Constitutional Change may, though it rarely does, affect the Reproductive Cell.Let us suppose that an average healthy man during his lifetime acquires, by use, accident, or disease, some change in his right arm. There is no reason to suppose that the sexual cells, rather than any other cells in the body, will be affected. If, on the other hand, this local change in the arm affects the blood, depriving it of nutritive power, or casting into it obnoxious matter, then it is possible that all the cells of the body may be affected. We have many instances of such a thing, as when the blood and whole constitution are involved after maybe a primary localaffection, and when, in consequence, the hair drops off, or marks and irregularities of the nails appear. In these cases the sexual cells may suffer from want of nourishment, or from what we may term a poison, and may produce less vigorous and perhaps diseased or malformed offspring, but they will show no tendency to develop in the offspring that primary local affection which caused ailment in the parent. But, as we shall see in thenext chapter, the sexual cells in most cases get off scot-free, and the most dangerous acquired constitutional diseases leave no trace of their passage upon the reproductive elements. It is indeed difficult to point to a case, with the notable exception of syphilis, in which acquired constitutional blood disorders leave any trace in the organisation of the progeny, and we are indeed fortunate that thisis so.There seems to be some evidence that we may stunt the growth of a plant or animal by insufficient or unsuitable food, and that all the cells of the body may thereby be reduced in size, the sexual cells among the rest, and that these reduced cells give rise to small progeny in the next generation. Here again the evidence in the case of animals seems rather doubtful, and rests on a few statements, such as that ofDe Quatrefages, that horses taken from Normandy to the hilly and less fertile country in Brittany become distinctly smaller in the course of three generations.In our own country large horses are found in the plains and small horses and ponies in the hilly districts of Wales and Scotland. But the obvious utility to man of small breeds in hilly districts, and of heavily-built horses on the plains, and the fact that horses have been bred for hundreds of years in view of their services to man, throws great doubt upon this particular evidence ofDe Quatrefages’, and we may well leave it out of account, unaccompanied as it is with evidence as to the total exclusion of the interbreeding of the Normandy with the Brittany variety.On the other hand, among plants it really appears as if by adjusting the soil and climate you may produce stunted varieties, whose seed produce small plants. The poor and exposed ground of our hilltops are covered with dwarfed varieties of the bigger plants growing luxuriously in the adjacent plains, and a classical case mentioned byLemaire[11]is that of the hemp which, removed from Piedmont to the less suitable soil of France, becomes a smaller variety, growing to only half its former height in the course of two or three generations. The enormous dwarfing that one can subject a plant to is illustrated in the case of the conifer, which the Japanese can cause to remain the size of a tiny shrub during its hundred years’ growth, by simply keeping the soil at the starvation edge, and by pruning the branches and roots.It appears then to be pretty certain that every man and woman possesses a store of sexual cells, derived directly from the original sexual cells from which he or she was developed. These in the main are like the original cell, being as they are of its substance, but they show minor differences amongst themselves, and give rise in their turn to offspring no two of which are alike. These sexual cells, residing within the paternal or maternal body, are uninfluenced by the course of life led by that body, except, perhaps, in some few cases in which the whole system and the blood are impoverished, saturated with alcohol, or infected with the microbes of disease, which microbes in some cases, perhaps, directly attack the sexual cells.The Facts of Evolutive Selection known to the Gardener and Breeder.Scientific men are often very slow at arriving at a truth, and there are many instances of valuable knowledge held by sections of the people in perhaps an empirical fashion, which has at last found acceptance by the learned. The practical results of all this biological teaching has been in the hands of cattle-breeders and nurserymen for centuries. The various breeds of cattle have been produced by man, not by any new method of ventilating the cow-sheds, or bysome freshly discovered patent fodder, but simply by selecting for breeding purposes those individuals that most suited the breeder’s purpose. The racing stallion was kept which most resembled a greyhound, the hog that most resembled a beer barrel, and the cow that gave the best combination of milk and flesh. The gardener produces the hundreds of new varieties placed every year in the market by keeping the seeds and propagating from any variety he may wish to perpetuate, and these varieties are always spontaneously occurring. He perfects his stock by selecting the seed only from the very best.The testimony not only of the learned but of those who in their lives, unbiassed by any theory, have been engaged in modifying breeds of animals and plants, is unanimously in favour of the view that selection is the only, or, at any rate, by far the most powerful factor in producing racial change. So far these facts have had little or no application to the question of human race progress. People are still too much biassed by archaic anthropocentric ideas; they view man by himself, under his own special laws, and would often be shocked by an attempt to draw obvious parallels between him and the lower animals. Amongst the thinking few this attitude has changed, and broader and sounder views are rapidly gaining ground.People, too, are apt to feel what may be called afalse delicacy in speaking of questions relating to race change, but this may more rightly be termed the shyness necessarily associated with an unusual topic of discussion. We English laugh at the American woman who, from notions of extreme modesty, will not speak of the “leg” of a piano; but we in our turn draw our own often exaggerated lines, beyond which we will not pass. Just as there is no subject which will not yield food for the evil-minded, so there is no subject—having to do with the laws of nature—which cannot be naturally approached in all simple-mindedness. As soon, therefore, as it is realised, that this question we are dealing with is one which demands not only our closest attention, but also the advantage of public and private discussion, so soon shall we have acquired the habit of regarding it in quite a matter-of-fact and pure-minded way.FOOTNOTES[2]“Franklin’s Miscellany,”p.9.[3]“Darwin and after Darwin,”vol.i.,p.257.[4]Chapter xxvii.,vol.ii., 1875.[5]“Life and Letters,”vol.ii.,p.14.[6]“Journal of the Anthropological Institute,”vol.v.,pp.344–7.[7]“Natural Inheritance” (1889),p.14.[8]“Studies in the Theory of Descent,” translated by Raphael Meldola,p.692.[9]“Essays upon Heredity,” translated by Poulton,Schönlandand Shipley;vol.i. published in 1889,vol.ii. in 1892.[10]Translated by W. Newton Parker (1893).[11]D’Orbigny’s“Dictionary.”CHAPTER III.CAUSES AND SIGNS OF PHYSICAL DETERIORATION.Modern Care for the Individual.Inthe last chapter we saw that while selection is an evident and powerful factor in the production of racial change, there is but slight and in many cases questionable evidence that acquired characters are ever transmitted. During their lifetime a man or woman may be subject to the most varied conditions, and yet the quality of his or her offspring will not be affected by these conditions except in cases where impoverishment or poisoning of the blood has ensued, thereby enfeebling his or her reproductive cells. These facts have not been gained by a study of the lower animals alone, for most researchers have kept man in view, while others, like Malthus and Galton, have confined their observations almost exclusively to the human kind. In this chapter we shall see how these generalisations are borne out by the study of disease, and we shall see what effect the modern methods for the treatment of the sickly and feeble are havingupon the race. We moderns as individuals have many advantages over those who have gone before us; we owe to the untiring energy of our ancestors the facilities for travel, the pleasures of accumulated music and literature,etc., but among these hundreds of advantages we possess none are more marked than those we owe to the scientific followers of the profession of medicine, the application of whose learning gives in our day to the less robust a possibility of life and happiness they never had before.Preventive Medicine.The words “mederi,” to heal, “medicus,” the healer, and “medicina,” the remedy, indicate pretty clearly the almost superstitious feeling current in early times regarding the attributes of the medical man; but physicians have in more recent years begun to doubt in some measure of their power to cure disease when once established. With increased knowledge, and with growth of professional acumen, the limits of this power are more clearly seen, and the solution of a metallic salt, or decoction of a herb is now withheld when at one time it would have been administered with the fullest confidence. With this healthy scepticism as to their power to cure has come very certain and exact knowledge of how to prevent, and preventive medicine has recently exercised aninfluence upon disease and upon mortality which is unique in the history of humanity. But while the benefit of our changed and more healthy surroundings are to the advantage of us all individually, we shall have to consider whether as a people we shall in the long run be the better for this change, or, on the other hand, whether in obtaining this individual advantage we are not imperilling the vigour of the race.Micro-organisms of Diseases and their Extermination.Nowhere has preventive medicine achieved greater triumph than in the extermination of certain micro-organisms which gain access to the body and cause the febrile class of diseases, such as small-pox, measles, typhoid fever, and very many others. At present none of these micro-organisms can be said to be extinct, but they have in some cases been banished to distant parts of the globe, and in other cases the conditions suitable to their existence, and the means of their propagation are so well understood that their banishment is being systematically and successfully carried out, so much so that a disease such as small-pox, which at one time headed the list of fatal diseases, does not come in the category of anxieties of the mother of to-day; and pyæmia and puerperal fever, which twenty years ago were at timesdreaded scourgers in most hospitals, now occur only from culpable and punishable neglect.The Reproductive Cells are as a Rule unaffected by them.A short study of these diseases should well repay us, showing as it will do that in by far the greater number of cases these severe constitutional derangements produce no effect upon the reproductive cells; that they are in fact incapable of producing a change that will be hereditarily transmitted. We shall learn, moreover, the part that they have played, and can play, in producing racial change by selection. The micro-organisms of disease are of many varieties, and each variety is capable of setting up its own peculiar disturbance. The disturbance set up by one kind we call small-pox, that arising from another kind, cholera, and so on. Now, the very curious point comes out that in most of these diseases, although the composition of the blood is profoundly altered, and many of the tissues undergo marked change, this change, fortunately for us, is quite of a temporary character, and when the attack is over there is only one test which will enable us to say that the body is not just in the same condition as it was before. This test is that it cannot be infected again for a long time, if at all, by the same micro-organism.This induced immunity from further attacks hasreceived in the hands ofMetschnikoffa curious and very interesting explanation. He has shown that an army of small cells, called phagocytes, which wander through the blood and tissues, are able to attack the microbes of disease, and that after a struggle they are able in many cases to kill these voracious invaders. In so doing, however, the weaker phagocytes succumb to the struggle, while those which are left alive within the body of the convalescent patient possess the power of resisting and destroying the particular microbe which had undertaken the invasion. These resisting phagocytes, selected from the rest, together with their descendants, who share their resisting qualities, are able to prevent fresh inroads of the same enemy. We need not, therefore, assume that this acquired immunity, the sole relic of the attack, indicates any change in the ordinary muscle or brain cells of the body, or that the reproductive cells are in any way altered, for the immunity is due only to a change in the phagocytic army.The germ cells in almost every case get off scot-free, and there is nothing in the organisation of a child to indicate whether or not his father or mother suffered from measles, or scarlet fever. It might at first sight be urged, in opposition to this fact, that, although we cannot recognise the child of a man who suffered from measles or scarlet fever by any visible sign, yet the child is in some way different, inasmuchas he is to some extent immune to those diseases. In favour of this belief, the many instances in which a fever has been brought to a country never before accessible to the germ (for instance, the introduction of measles and small-pox to newly discovered America, where fearful ravages were caused thereby), may be brought up as evidence to prove that those habitually living among the germs must have become immune and have transmitted this immunity to their progeny. Again, the black population of Sierra Leone have only a mortality of 24 percent.from malaria, while the mortality of the white settlers is 47 percent.;[12]and, in this case, it may be urged that the black race has become by transmission of immunity partially immune. But these cases which appear to be examples of transmitted immunity may receive another, and a much more simple, explanation. No two children of the same parents are alike in colour of hair, shape of limb, temperament,etc., and they also differ widely in their capacity to receive and combat infection. An epidemic of fever, therefore, will always select to kill those organically most liable to fall a prey to it, while the remnant, having by nature greater power of resistance, not only survive, but may also be calculated upon to produce progeny, on the whole, as resistant as they are themselves.Man has been selected by the Action of the Microbes of Fever.Races, therefore, subject to epidemics of a particular fever, suffer selections in the hands of the microbe of that particular fever, and those living are survivals cast in the most resisting mould. It may not be flattering to our national vanity to look upon Englishmen as the product of the selection of the micro-organisms of measles, scarlet fever, small-pox,etc., but the reasonableness of the conclusion seems to be forced upon us when we consider his immunity from these diseases as compared with that of natives of the interior of Africa, or of the wilds of America, whose races have never been so selected, and who, when attacked for the first time by these diseases, are ravaged almost to extermination. We find, then, that an ordinary attack of measles, scarlet fever, whooping cough, erysipelas, typhoid, or typhus fever, when it has passed away, leaves the tissues of the body in as sound and healthy a condition as before; and, indeed, were it not for this fact, the human race could hardly have existed at all, continually exposed as it has been, for countless ages, to the aggressions of these microbes. By exterminating these diseases, we shall, no doubt, preserve countless lives to the community, who will in their turn become race producers, but, inasmuch as the individuals thus preserved will inmany cases belong to the feebler and less resisting of the community, the race will not become more robust. In fact, it is probable that, as a race, we shall thereby suffer, for the banishment of the disease will enable the feebler members of the community to live, and in larger proportion contribute to the progeny of the future. That this is actually the case will shortly bepointed out.Leprosy an Exterminator of the Unhealthy.But there are other microbes which, in addition to the production of blood changes, have a profound and lasting effect upon many of the tissues of the body. Such are the microbes of leprosy and syphilis.The terrible ravages that the microbe of leprosy is capable of effecting are appreciated only by those who in Norway or elsewhere have visited those death-houses now fortunately to be found in but one or two parts of Europe. Yet, even in this case, strange to say, the germ cells do not seem to be reached by this loathsome disease, and it is not transmitted from parent tochild.[13]A disease of mediæval, not of modern, Europe, we need not discuss its action on racial change more than to say that, hideous as are its aspects, it must be looked upon as a friend to humanity; for, while the microbe of typhoid fever will attacka man who is healthy and living in healthy surroundings—excepting for the microbe that lurks in his well—the microbe of leprosy feeds upon those who are debilitated by conditions under which healthy and strong racial development is impossible. It is a depopulator of starved, ill-nourished districts, and the race recruits to its advantage from those more favourably placed.In the case of syphilis, serious and often permanent tissue change is produced as a result of the action of the microbe, and in this disease, to an absolute certainty, an effect may be produced upon the offspring. Many suppose that this is due to the transmission of the specific microbe itself from the body of one or both of the parents to the developing egg. That such a thing is not impossible is shown in the case of silk-worm disease, in which the spores are to be found within the egg of the silk-worm moth. These spores subsequently develop and attack the tissues of the grub of the next generation. In syphilis the same kind of thing no doubt occurs; for a syphilitic child may subsequently infect the mother or nurse during the period of suckling. But there are other cases in this disease which appear hardly to be explained so easily, and we have to assume that the germinal cells are themselves changed in some way during their sojourn in the parental body, for after a certain time the disease is no longer capable of transmissionby the parent, and the children born after this period, though themselves diseased, are incapable of infecting those who tend them. We have every reason to believe, therefore, that there are no specific germs or microbes left in the body of the parent, and that we have to do solely with the more or less permanent change in the reproductive cells, produced by the microbes during their residence in the body of the parent. The children born during this period are frequently ill-nourished, possess recognisable indications of disease, and are subject to nervous and other affections.We have here, therefore, for the first time, distinct evidence that an obviously acquired constitutional disease is transmitted, and that that transmission is in some cases due to a direct effect of the action of the microbe upon the germinal cells. The microbe of syphilis, unlike the microbe of leprosy, but like that of measles, feeds on healthy blood and tissue. It attacks the strong as well as the weak, and, if the weak more readily succumb, yet the strong and vigorous are more apt to acquire it. It is not, therefore, selective, like leprosy, and this fact, added to that of its capacity of transmission, ranks it as a disease distinctly inimical to race progress.Germs of Phthisis and Scrofula, our Racial Friends.During recent years it has been discovered that the symptoms of phthisis and scrofula are due to a microbe, the tubercle bacillus. It appears, however, that this bacillus cannot gain access to, or multiply in, the tissues of a healthy and vigorous man or woman; most of us probably have often carried this micro-organism within the mouth or stomach, and though our gastric juice has not been able to destroy it, as is the case with so many of our invisible foes, it has been unable to pass into our blood or lacteals.Dr.Woodhead puts this factstrongly.[14]He says: “A perfectly healthy individual, placed under favourable conditions as regards food, fresh air, and exercise, is never attacked successfully by tubercle bacilli, the active, vigorous tissue cells being perfectly able to destroy any bacilli that make their way into the lungs, the pharynx, or the intestine.”It appears, too, that a certain type of individual is readily attacked by this microbe, while the normal individual, debilitated though he may be by unfavourable external conditions, falls far less readily a victim. AsProf.Sir LauderBrunton[15]remarks: “We are constantly meeting with persons belongingto very consumptive families who escape the disease by living under conditions where the bacillus tuberculosus is likely to be absent. On the other hand, persons such as nurses are in all probability frequently inhaling the microbe, and yet are not attacked by the disease. In the first case immunity is probably due to the absence of the seed, notwithstanding the favourable condition of the soil; in the second it is due to the barrenness of the soil, notwithstanding the presence of the seed.”Inasmuch as phthisis is markedly hereditary, we may look upon thetype, not the disease, as being transmitted. A phthisical type of person is one who comes of a family liable to fall a prey to this microbe, and he is recognisable by many distinctive characteristics of hair and complexion, and by qualities of temperament, feature, and figure.Sufferers from phthisis are prone to other diseases, such as pulmonary and bronchial attacks, so that over and above the vulnerability to this one form of microbe they are to be looked upon as unsuited not only for the battle of life, but especially for parentage and for the multiplication of the conditions from which they themselves suffer.The phthisical are attractive in personal appearance on account of their rich skin and hair colouring and their frequent brightness and vivacity, and their obvious delicacy also elicits a feeling of pity andwish to protect them. In consequence of this they easily marry, and they are as a rule very fertile.Galton[16]says: “There is fair doubt whether a group of young persons destined to die of consumption contribute considerably less to the future population than an equally large group who are destined to die of other diseases.” Now this phthisical type is very common with us indeed, and it appears to be an innate variation to which our race is liable. It is evident, therefore, that those people with the tuberculous variation who, even under the present circumstances, manage to contribute their quota to the population, would, were the bacillus tuberculosus altogether exterminated, contribute more than their share, and the type would become more common. And let it be remembered that this type, apart from the action of the bacillus, is a delicate and fragile one and liable to other affections, and the effect of giving the type any advantage in the struggle for life would surely imperil the well-being of the future of the race. When, some years ago, it was thought that a cure for phthisis had at last been obtained, great tribute was naturally and rightly paid to its discoverer; but had this cure proved as efficient as the more sanguine were led to expect, it would be terrible to contemplate the eventual suffering that would have resulted from the constantly increasingnumbers of the phthisical type that would have been born with each generation.If we stamp out Infectious Diseases we perpetuate Poor Types.It is a hard saying, but none the less a true one, that the bacillus tuberculosus is a friend of the race, for it attacks no healthy man or woman, but only the feeble. It is like the bacillus of leprosy in this respect, but in this respect only, for leprosy attacks anyone living under certain unhygienic conditions. Remove these conditions—as we have done long ago—and the bacillus of leprosy disappears; its duties are over, like those of the extinct plants and fishes in the rocks.The tubercle bacillus on the other hand attacks a type to be found not only in the poor, ill-fed, and ill-conditioned, but also those who live well. It is a disease of all classes, and those who live in well-ventilated rooms, and who conform to every sanitary regulation, may still belong to the type who fall a prey to it. It is certain, therefore, that, improve the external conditions of life how you will, this type will remain. It is also as certain that in giving the type a better chance than it has already, by preventing infection or by delaying the disease, the type will be more and more prevalent as each generation comes to life.It comes out pretty clearly from our short study of the infective diseases that some of the microbes that cause these, such as the bacillus of tubercle, only feed on unhealthy human tissue, while the greater number of them kill, if anything, the weak rather than the strong. They are, therefore, on the whole, and as a natural consequence, our race friends rather than our foes, and if we attempt seriously to do away with their selective influence—viz., the elimination of the weak and the preservation of the strong—we must supply this selective influence by one equally potent, or the race will tend to deteriorate. What can be done in the future, and what it is expedient for us to do at the present time, will be more fully discussed in a subsequent chapter; but I may state at once thatpari passuwith our endeavour to prevent these diseases must be our efforts to enlist the co-operation of the human charity that would avert suffering in such selection as shall necessitate the birth of future generations from the healthiest and best of those amongst us. As selection is the race-changer, we must replace the selection of the microbe by the selection of human forethought.A number of diseases, which are due probably to innate family predispositions, are known to us. Of these diabetes, hæmophilia, and some others are of comparative rarity, and may be left on one side inthis necessarily contracted sketch. Others, such as cancer and constitutional weakness of the respiratory and other organs, as well as insanity, are frequent enough to merit our close attention. Of cancer we at present know too little, and I propose to leave it on one side. Of inherited weakness of special systems we have many examples, such as a delicate respiratory or digestive mucous membrane, inherited variations in the mechanism of assimilation, and also gout and obesity—in fact, innate delicacy of all kinds, which renders their possessor less able to cope with his natural surroundings, let these be whatthey may.There is hardly a family that can boast of the complete want of hereditary weakness, and among the children of particular families, where these weaknesses exist, some show the taint more than others. In times of hardship, cold, exposure, coarse food,etc., these weaker ones perish, and the race is consequently propagated from the stronger ones. Within certain limits cold, exposure and coarse food are compatible with great physical excellence, for the cold and exposure, hurtful to the sickly, braces and hardens the more robust, and coarse but nutritive food supplies him with energy and strengthens the powers of digestion. The finest races have been bred by hardship. It is proverbial to speak of “the hardy mountaineer,” and one cannot look at a lowland Scot without feeling that his stock had, in daysgone by and for many centuries, run the gauntlet of oatmeal porridge and cold east wind.But we are rapidly diminishing those selective agencies which in the past have developed race vigour. As we shall presently see, skill in nurturing the sickly has, in modern times, wonderfully reduced the mortality amongst infants; improvements in methods of nursing, the replacement of cotton by flannel and wool, and the use of many foods, some of them artificially digested, gives a sickly infant a chance of living, and it survives its first most dangerous years. Then its chances are again improved, for the infective diseases are being held in check, and it has comparatively little to fear from them. Thus it survives and lives to adult age, when, like the hothouse plant, it is still protected from hardships to which the race had formerly been freely exposed. It lives to lower the average physique of the mothers or fathers who produce the next generation of children.This increased preservation of the sickly has had the effect of increasing the life period of an average child, and this increase in the life probability is often and very rightly cited as an indication of the improved sanitary conditions of the people. Improved sanitary surroundings, as we have seen, are taken advantage of chiefly by the sickly, and thus with our increased probability of life we have diminishedthe average robustness of constitution, or innate healthiness of the race, for a larger proportion of sickly ones are living amongst us. In our day a greater number of parents suffer from phthisical, scrofulous and other taints than in days gone by, and these and other taints are passed on to their children.So far we have seen what of necessity follows from our biological premises, but it is also possible, I think, to show by statistics that already very observable deterioration has taken place.Births, Deaths, and Marriages.If we examine one of the reports of the Registrar General for births, deaths and marriages, we shall gain pretty full information concerning the deaths from disease, accident, old age,etc., that have occurred during the last thirty or forty years.Increase of Constitutional Weakness.In Report 54, Table 17, the annual death-rates from various causes per million of population are given, and arranged in groups of five years from 1858 to 1890. We have there a history of thirty years, and even in that time a notable change in thishistory is to be observed. I have arranged the greater number of facts given in Table 17 in the following table, so as best to bring out those points which we are discussing. In the first group of disease are those due to micro-organisms, and a diminution of these diseases to a marked extent is to be observed of late years. Phthisis and scrofula placed by themselves in this group share in this decrease. In the second group are diseases that are due in great measure to carelessness, want of management, neglect and ignorance, such as convulsions, diseases of dentition, parturition and registered accidents. These, too, as one would expect, diminish yearly in a country where surrounding comforts and a sense of responsibility are on the increase. When we turn to the third group, that of constitutional disease, where the hereditary tendency comes in, we find an increase in almost all the hereditary diseases. A tendency to an increase of neurotic affections is shown by an increase in the deaths from nervous diseases, suicide and intemperance. A large increase in the diseases of the respiratory system is due in part to the increasing number of tuberculous patients who, kept from inroads of microbes, nevertheless readily fall a prey to other affections: there is, too, an increase in diseases of the circulatory system, in cancer, diabetes and other constitutional diseases.Annual death-rates in England from various causes, per million persons living, in groups of years1858–1890—[Version of the table for narrower screens]CAUSE OF DEATH.1858–60.1861–65.1866–70.1871–75.1876–80.1881–85.1886–90.GROUP I.Phthisis and scrofula3304·03311·03300·22940·62816·82540·82322·2Other diseases of micro-organisms[17]4403·94498·64677·24055·83233·62708·82417·0GROUP II.Diseases of dentition, parturition, convulsions, accident and negligence2257·02262·02191·02077·21860·41678·61538·0GROUP III.Some consti­tutionaldiseases[18]6056·36311·46594·671997536·47531·27929·4

Fig.1.Diagram to illustrate:A, the transmission of acquired characters,B, modification of type by natural selection. InAan individual of rounded proportions, at the top of the diagram, has two children. Environment is represented by a board with holes through which they must pass. In so doing they become thinner, transmit the thinness to their children, and so on. InB, a man of rounded proportions has two sons who vary, one being fat, the other thin. The fat one cannot get through the hole in the board; but the thin one does, has children who again vary, the thin one having an advantage.

Fig.1.

Fig.1.

Diagram to illustrate:A, the transmission of acquired characters,B, modification of type by natural selection. InAan individual of rounded proportions, at the top of the diagram, has two children. Environment is represented by a board with holes through which they must pass. In so doing they become thinner, transmit the thinness to their children, and so on. InB, a man of rounded proportions has two sons who vary, one being fat, the other thin. The fat one cannot get through the hole in the board; but the thin one does, has children who again vary, the thin one having an advantage.

Now there are three ideas in this law of natural selection: first, that there are inborn variations among the offspring even of the same family; secondly, that these various individuals living in surrounding conditions on the whole uniform and common to all of them, will start in life, some with an advantage and others with a relative disadvantage, and that those possessing an advantage will, more of them, tend to produce offspring; thirdly, that the variations, inborn in this case and not acquired, will probably be transmitted. That there are marked variations—physical, mental, and moral—among a litter of kittens or puppies is within the experience of everyone who has kept them, and that variations in human families are as marked is known to everyone who has brothers and sisters. Even twins frequently differ considerably from each other, and it is said that the last years of the lives of the Siamese twins were sadly marred by their opposing views as to the rights and wrongs of the American Civil War! It stands to reason also that these variations may be of advantage or disadvantage to their possessors, and that among animals and plants, where there are no social props given to the weak, the variations may and do determine survival. To give an idea of the rigorous operation of selection which we find among the loweranimals, we have only to enumerate the number of the progeny produced by each pair, which is often prodigious, and knowing as we do that the number of individuals in a species remain virtually the same in a given district for long periods of time together, we conclude that the room of the parents is just filled by a younger pair, and all the excess of their progeny over and above this one pair must have succumbed to surrounding want and hardship. To give one concrete example out of hundreds that might be selected, let us take the case of the golden eagle given by Weismann in his essay on the “Duration of Life.” He says: “Let us fix the duration of life in the golden eagle at sixty years, and its period of immaturity (of which the length is not exactly known) at ten years, and let us assume that it lays two eggs a year, then a pair will produce one hundred eggs in fifty years, and of these only two will develop into adult birds, and thus on an average a pair of eagles will only succeed in bringing a pair of young to maturity once in fifty years; and so far from being an exaggeration, this calculation rather under-estimates the proportion of mortality among the young.”

But in all probability most of us are more conversant with the ways of the domesticated cat than with those of the golden eagle. The cat produces its first litter of three or four before it is a year old. Itskitten-producing life lasts, say, for eight years, and it may, on a low estimate, be supposed to produce a litter of four kittens once in each year. In all a cat will have, on a fair estimate, thirty-two kittens, and may be a great-great-great-great-great-great-grandmother in her lifetime, yet we do not observe in town or village such an alarming increase in the cats from year to year. Their number is pretty stationary, kept so by the enormous destruction of their progeny. The enormous capacity for reproduction of a race of animals, where for a time their surroundings are favourable, will be appreciated by the lowland farmers whose fields were laid waste a few years ago by armies of short-tailed field-mice, whose natural enemies, the hawks, the cats, and the weasels, had been extensively shot or trapped.

The struggle to survive among the savage tribes of man must be excessive. Whole races come and go, and their survivors again fall victims to privations, disease, or natural enemies, before the white man with his better brain and capacity for adaptation.

The third idea in the law of natural selection—namely, that inborn variations are transmitted—is also a fact that is universally admitted not only among biologists at the present day, but by thosewho trust only to their everyday experience. “The child has its father’s temper,” or “its mother’s eyes,” are expressions heard in every nursery, while the innumerable cases of the transmission of inborn drooping eyelids and supernumerary fingers and toes show the same thing in a more striking manner.

The law of selection is therefore no mere unproved fancy, it is a statement of fact, and of one which is so obviously true that it is now almost universally admitted, not only among specialists, but by most intelligent and educated persons. It was understood, and its significance partly appreciated by Malthus, and I find that even he acknowledges a prior claim ofFranklin’s.[2]Romanes[3]tells us that the idea occurred in 1813 toDr.Wells, and in 1831 toMr.Patrick Matthew, and the wonder is that other thinkers have passed unnoticed such an obvious phenomenon.

While, however, natural selection as an agent capable of producing racial change is accepted by almost every well-instructed biologist, there are some who are still inclined to give some value to the operation of the Lamarckian transmission of acquiredcharacters. They do not deny that to selection is due by far the most obvious racial changes, and that experimentally the most potent factor in the production of a new variety of a plant or animal is selection. They are, however, inclined to believe that along with this, there may be some transmission of acquired character, only discernible after the lapse of many generations. Darwin himself thought that this was the case; he held that certain racial distinctions were due to the action of the environment on the parents and the transmission of the change thus produced upon their offspring. In his great work upon “The Variation of Animals and Plants underDomestication,”[4]he enumerates some of these. They may be divided roughly into two classes: first, instincts and habits; and, secondly, results of use and disuse. Darwin believed that the trained habits of dogs and horses, the tameness of the rabbit and other domestic animals, were due to the direct and transmitted effects of man’s contact. He held that the large size of the leg and small size of the wing of the domestic as compared with the wild duck are gradually acquired and transmitted by use and disuse.

But Darwin, as Huxley pointsout,[5]was inclined to lay less stress upon the transmission of acquiredcharacters in his later writings; and we find that in the “Origin of Species” he is inclined to abandon them altogether, and accept the position now held by the Neo-Darwinian School of Galton and Weismann. He says (pp.117, 118), “If under changed conditions of life, a structure, before useful, becomes less useful, its diminution will be favoured, for it will profit the individual not to have its nourishment wasted in building up useless structures.... Thus, I believe, natural selection will tend in the long run to reduce any part of the organism as soon as it becomes through changed habits superfluous.”

Just as Darwin himself, as time went on, laid more and more stress upon the importance of selection, and less and less upon the transmission of acquired characters, most naturalists have tended to follow him in the same direction. It may be said, I think, without gainsay, that, since Darwin’s death, the most important and outstanding work done by the biologists has been the uprooting of much of the Lamarckian doctrine, originally held, not without question, however, by Darwin himself. The biologist of to-day is more Darwinian than Darwin, and explains on the Darwinian hypothesis even those cases which had presented difficulties to Darwin’s own mind.

Amongst those who were pioneers are Galton and Weismann, and, curiously enough, in England and Germany these two men, independently of each other, came to the same conclusion respecting the non-inheritance of acquired qualities, and pointed out that the facts of development indicate that the generative matter is passed on from one generation to another, remaining intact in the body of the parent, and that we have no reason to suppose that it could be influenced by changes in other parts of the parental organism. It is not uninteresting to note and contrast in these two investigators the action of the typically English and typically German mind, more especially as the comparison is perhaps equally complimentary to the two nationalities, and indicates the value of results arrived at by workers of different individualities.

Galton was first in the field, and as long ago as1876[6]made the following clear and concise statement:—“The conclusion to be drawn from the foregoing arguments is that we might almost reserve our belief that the structural cells can react on the sexual elements at all, and we may be confident that at most they do so in a very faint degree: in other words,that acquired modifications are barely, if at all, inherited in the correct sense of the term.” Thirteen yearslater[7]he expresses himself in practically the same terms. An untiring investigator, chiefly in the facts of human heredity, he briefly sums up as above one of his most important general conclusions. It is all he has to say, it is all that his facts permit himto say.

In 1882, Weismann[8]questioned whether there is as yet any proof that acquired characters are transmitted; he writes:—“The theoretical conception of variation as a reaction of the organism to external influences has also not yet been experimentally shown to be correct. Our experiments are still too coarse, as compared with the fine distinctions which separate one individual from another, and the difficulty of obtaining clear results is greatly increased by the circumstance that a portion of the individual difference always depends upon heredity, so that it is frequently not only difficult, but absolutely impossible, to separate those which are inherited from those which are acquired.”

Since that time, Weismann, in a series of importantessays,[9]indicating a profound knowledge not only ofcomparative morphology, but of the habits and modes of life of a vast number of animals and plants, has shown that many of the cases which Darwin was doubtful about may reasonably be explained by selection, and he has marshalled a vast mass of evidence in support of the argument that acquired characters, experimentally produced, are not transmitted.

These essays are profoundly interesting, and will supply food for thought for many years, but it must be admitted that Weismann has gradually been led away to speculations of the most elaborate kind, built upon the most flimsy substratum of fact. There is evidence of this tendency even in his early writings, but in his later essays, especially his recent work on “The Germ Plasm: a Theory ofHeredity,”[10]the speculative part quite overpowers the rest.

As those who are interested in heredity will probably read his works with the greatest attention, I have ventured in anappendixto make clear what in his works may, in my opinion, safely be looked upon as speculative rather than legitimate, or even provisional, generalisation, and what, therefore, may be altogether omitted from the study of a practical problem such as that with which we are concerned.

The practical issues which both Galton and Weismann have raised cannot, however, be underestimated, and, in respect to the non-inheritance of acquired characters, the mass of modern thinkers may already be said to have given their allegiance to the views of those two thinkers.

But we are living in times when mere authority is at a discount, and we may well demand the facts for ourselves. The point which we are inclined to question is one as to which a doubt was often present in Darwin’s mind. Granted that selection is a factor, we are inclined to believe that the transmission of acquired characters must also take place, at any rate, to some extent. In attempting to decide this question upon the facts themselves we may take two lines of research. In the first place, we may examine every case of racial change, the production of new or different parts, the development of a new instinct, or the degeneration or loss of parts or instincts present at some past epoch. If in every case we are not compelled to exclude natural selection, and if in every case that we can directly and experimentally follow, selection is the outstanding factor, then there is strong presumptive evidence that racial change is caused by selection and not by the inheritance of acquired characters. In the second place, we mayartificially induce the acquisition of some character, and notice whether this is transmitted; if it is not, then the general operation of this kind of transmission is rendered very doubtful.

It is upon these two lines that Galton and Weismann worked, and we may now follow in rough outline the evidence they adduced. Darwin had been able to explain, to universal satisfaction, the evolution of many types and varieties, as a result of selection alone; though certain cases of the supposed inheritance of use and disuse, and of acquired instincts, caused at times doubts to arise in his mind. But Weismann has questioned this inheritance, and has shown that—as Darwin himself sometimes believed—these may readily be explained by selection alone. The gradual increase, generation after generation, in the size of a useful limb or the perfection of a valuable organ of sense may readily be explained by selection. The fact that the limb or organ is of use to the race in its struggle will determine the survival of those born with these serviceable parts well-formed, and these in their turn will produce others as favourably or more favourably constituted, from whom further selection can take place. We cannot shut our eyes to theoperation of selection in such instances, nor have we any reason for saying that part of the effect must be due to some other cause. In the case of organs which become useless and finally disappear in the course of generations, a selective agency will sufficiently account for this disappearance. As Darwin himself pointed out, a useless organ is an expense and a drain upon an animal’s capital; it requires blood, and its exercise uses up some of the sum total of energy the animal possesses. The truth of this can be shown experimentally, as when compensatory growth occurs in the rest of the body after amputation of a limb, or when one lung or kidney enlarges subsequently to the disease or removal of the other. In cases where an organ is useless, those who have it badly developed, and in consequence have other and useful parts more fully formed, will have a distinct advantage over those born with a well-formed but useless organ. We may thus explain the small size of the wings of the tame as compared with the wild duck, an instance in which Darwin saw difficulty in excluding inherited disuse. In this way we may explain the occurrence of the still smaller wings of the running ostrich and apteryx; also the blind fish of the Kentucky Cave, and the visionless eyes of the burrowing mole. As an illustration, an animal or man may, in this respect, be compared to an individual with a given amount of capital, who,if he spends his money in one direction, will thereby have less for another purpose. In this way a big leg may be obtained at the expense of a small arm, or a good ear be the cause of anindifferent eye.

When we turn to the question of the supposed transmission of acquired instincts and habits, we find that it is possible by means of the principle of selection, to explain some, at least, of the cases which presented difficulties to Darwin’s mind. Thus the tameness of rabbits, cats, and dogs, which animals have for countless generations been subjected to domestication, need not necessarily be accounted for by supposing that the results of training are transmitted. For it is easy to understand how those that would have rebelled most against man’s authority, and who were by nature the least tractable, would have been less cared for by man, and probably would finally have suffered extermination, while the docile received his attention, and were allowed to reach maturity and perpetuate the race. That this selection must be going on at the present time is very obvious, and as instances we may note the savage dogs that are constantly being destroyed, and the house dogs and domestic pets that are, in most cases, continually being selected from the docile animals and those of good temper. A dog that does not possess these good qualities can have no existence in town or village, and so by continualextermination of the unfriendly, the “friend of man” has gradually been evolved.

Turning now to those cases in which characters can be acquired or experimentally stamped upon an individual, we find that no single reliable instance can be adduced in which transmission takes place. Mutilations have been practised upon male infants by Jews and other Semitic races for thousands of years; yet, in spite of this, the operation has still to be performed, for the lost parts appear in the offspring of to-day as in the earlier periods of their race’s history. Certain breeds of dogs and sheep have for many generations been systematically docked, and yet the young are born with as long tails as those of other breeds. Chinese women have compressed their feet from times long past in their history, yet Chinese female infants are still born with large feet, and have to undergo afresh the torture of their compression. More curious still, for it affects an organ of paramount importance, the brain, there is a tribe of Indians who flatten their heads in early life, entirely changing the shape not only of the skull, but of the brain itself, yet their children are born with normal rounded heads; the induced change is not transmitted.

It must be admitted that this evidence is pretty strong, and we need not wonder that it has produced such widespread conviction, although it has been so lately taken up by the thinking public.

The body of a plant or animal is composed of small living bodies, most of them of microscopic size, called cells. These lead, to a certain extent, individual lives, and have individual characters, but they are built, as it were, together, like the bricks and stones of a house, to form the body. The cells are, all of them, nourished by the blood and lymph, and some are connected together by strands of connecting matter termed nerves. All the cells of the body are descendants from a single fertilised egg, which has resulted from the fusion of a paternal and maternal sexual cell. Among the cells of the body, and situated in special organs, are the sexual cells, likewise nourished by blood, but not connected by nerves with other parts of the body.

Now there is no reason to suppose that these sexual cells residing in the bodies of the parent willbe influenced by a change in the muscle or brain cells of the parent unless this change in some way or another influences the blood, the common go-between. But the blood is now known to be but a food and oxygen carrier, and an eliminator of used-up products. It is like a river laden with vessels carrying corn for the food of the big city, and nothing more. The life, the energy, the character of the body is the sum of the lives, the energies, and the characters of the cells—although these necessarily require the nourishment derived from healthy blood—just as the life of the city is the sum of the life of its citizens who require the nourishment of the corn.

Let us suppose that an average healthy man during his lifetime acquires, by use, accident, or disease, some change in his right arm. There is no reason to suppose that the sexual cells, rather than any other cells in the body, will be affected. If, on the other hand, this local change in the arm affects the blood, depriving it of nutritive power, or casting into it obnoxious matter, then it is possible that all the cells of the body may be affected. We have many instances of such a thing, as when the blood and whole constitution are involved after maybe a primary localaffection, and when, in consequence, the hair drops off, or marks and irregularities of the nails appear. In these cases the sexual cells may suffer from want of nourishment, or from what we may term a poison, and may produce less vigorous and perhaps diseased or malformed offspring, but they will show no tendency to develop in the offspring that primary local affection which caused ailment in the parent. But, as we shall see in thenext chapter, the sexual cells in most cases get off scot-free, and the most dangerous acquired constitutional diseases leave no trace of their passage upon the reproductive elements. It is indeed difficult to point to a case, with the notable exception of syphilis, in which acquired constitutional blood disorders leave any trace in the organisation of the progeny, and we are indeed fortunate that thisis so.

There seems to be some evidence that we may stunt the growth of a plant or animal by insufficient or unsuitable food, and that all the cells of the body may thereby be reduced in size, the sexual cells among the rest, and that these reduced cells give rise to small progeny in the next generation. Here again the evidence in the case of animals seems rather doubtful, and rests on a few statements, such as that ofDe Quatrefages, that horses taken from Normandy to the hilly and less fertile country in Brittany become distinctly smaller in the course of three generations.In our own country large horses are found in the plains and small horses and ponies in the hilly districts of Wales and Scotland. But the obvious utility to man of small breeds in hilly districts, and of heavily-built horses on the plains, and the fact that horses have been bred for hundreds of years in view of their services to man, throws great doubt upon this particular evidence ofDe Quatrefages’, and we may well leave it out of account, unaccompanied as it is with evidence as to the total exclusion of the interbreeding of the Normandy with the Brittany variety.

On the other hand, among plants it really appears as if by adjusting the soil and climate you may produce stunted varieties, whose seed produce small plants. The poor and exposed ground of our hilltops are covered with dwarfed varieties of the bigger plants growing luxuriously in the adjacent plains, and a classical case mentioned byLemaire[11]is that of the hemp which, removed from Piedmont to the less suitable soil of France, becomes a smaller variety, growing to only half its former height in the course of two or three generations. The enormous dwarfing that one can subject a plant to is illustrated in the case of the conifer, which the Japanese can cause to remain the size of a tiny shrub during its hundred years’ growth, by simply keeping the soil at the starvation edge, and by pruning the branches and roots.

It appears then to be pretty certain that every man and woman possesses a store of sexual cells, derived directly from the original sexual cells from which he or she was developed. These in the main are like the original cell, being as they are of its substance, but they show minor differences amongst themselves, and give rise in their turn to offspring no two of which are alike. These sexual cells, residing within the paternal or maternal body, are uninfluenced by the course of life led by that body, except, perhaps, in some few cases in which the whole system and the blood are impoverished, saturated with alcohol, or infected with the microbes of disease, which microbes in some cases, perhaps, directly attack the sexual cells.

Scientific men are often very slow at arriving at a truth, and there are many instances of valuable knowledge held by sections of the people in perhaps an empirical fashion, which has at last found acceptance by the learned. The practical results of all this biological teaching has been in the hands of cattle-breeders and nurserymen for centuries. The various breeds of cattle have been produced by man, not by any new method of ventilating the cow-sheds, or bysome freshly discovered patent fodder, but simply by selecting for breeding purposes those individuals that most suited the breeder’s purpose. The racing stallion was kept which most resembled a greyhound, the hog that most resembled a beer barrel, and the cow that gave the best combination of milk and flesh. The gardener produces the hundreds of new varieties placed every year in the market by keeping the seeds and propagating from any variety he may wish to perpetuate, and these varieties are always spontaneously occurring. He perfects his stock by selecting the seed only from the very best.

The testimony not only of the learned but of those who in their lives, unbiassed by any theory, have been engaged in modifying breeds of animals and plants, is unanimously in favour of the view that selection is the only, or, at any rate, by far the most powerful factor in producing racial change. So far these facts have had little or no application to the question of human race progress. People are still too much biassed by archaic anthropocentric ideas; they view man by himself, under his own special laws, and would often be shocked by an attempt to draw obvious parallels between him and the lower animals. Amongst the thinking few this attitude has changed, and broader and sounder views are rapidly gaining ground.

People, too, are apt to feel what may be called afalse delicacy in speaking of questions relating to race change, but this may more rightly be termed the shyness necessarily associated with an unusual topic of discussion. We English laugh at the American woman who, from notions of extreme modesty, will not speak of the “leg” of a piano; but we in our turn draw our own often exaggerated lines, beyond which we will not pass. Just as there is no subject which will not yield food for the evil-minded, so there is no subject—having to do with the laws of nature—which cannot be naturally approached in all simple-mindedness. As soon, therefore, as it is realised, that this question we are dealing with is one which demands not only our closest attention, but also the advantage of public and private discussion, so soon shall we have acquired the habit of regarding it in quite a matter-of-fact and pure-minded way.

[2]“Franklin’s Miscellany,”p.9.

[3]“Darwin and after Darwin,”vol.i.,p.257.

[4]Chapter xxvii.,vol.ii., 1875.

[5]“Life and Letters,”vol.ii.,p.14.

[6]“Journal of the Anthropological Institute,”vol.v.,pp.344–7.

[7]“Natural Inheritance” (1889),p.14.

[8]“Studies in the Theory of Descent,” translated by Raphael Meldola,p.692.

[9]“Essays upon Heredity,” translated by Poulton,Schönlandand Shipley;vol.i. published in 1889,vol.ii. in 1892.

[10]Translated by W. Newton Parker (1893).

[11]D’Orbigny’s“Dictionary.”

Inthe last chapter we saw that while selection is an evident and powerful factor in the production of racial change, there is but slight and in many cases questionable evidence that acquired characters are ever transmitted. During their lifetime a man or woman may be subject to the most varied conditions, and yet the quality of his or her offspring will not be affected by these conditions except in cases where impoverishment or poisoning of the blood has ensued, thereby enfeebling his or her reproductive cells. These facts have not been gained by a study of the lower animals alone, for most researchers have kept man in view, while others, like Malthus and Galton, have confined their observations almost exclusively to the human kind. In this chapter we shall see how these generalisations are borne out by the study of disease, and we shall see what effect the modern methods for the treatment of the sickly and feeble are havingupon the race. We moderns as individuals have many advantages over those who have gone before us; we owe to the untiring energy of our ancestors the facilities for travel, the pleasures of accumulated music and literature,etc., but among these hundreds of advantages we possess none are more marked than those we owe to the scientific followers of the profession of medicine, the application of whose learning gives in our day to the less robust a possibility of life and happiness they never had before.

The words “mederi,” to heal, “medicus,” the healer, and “medicina,” the remedy, indicate pretty clearly the almost superstitious feeling current in early times regarding the attributes of the medical man; but physicians have in more recent years begun to doubt in some measure of their power to cure disease when once established. With increased knowledge, and with growth of professional acumen, the limits of this power are more clearly seen, and the solution of a metallic salt, or decoction of a herb is now withheld when at one time it would have been administered with the fullest confidence. With this healthy scepticism as to their power to cure has come very certain and exact knowledge of how to prevent, and preventive medicine has recently exercised aninfluence upon disease and upon mortality which is unique in the history of humanity. But while the benefit of our changed and more healthy surroundings are to the advantage of us all individually, we shall have to consider whether as a people we shall in the long run be the better for this change, or, on the other hand, whether in obtaining this individual advantage we are not imperilling the vigour of the race.

Nowhere has preventive medicine achieved greater triumph than in the extermination of certain micro-organisms which gain access to the body and cause the febrile class of diseases, such as small-pox, measles, typhoid fever, and very many others. At present none of these micro-organisms can be said to be extinct, but they have in some cases been banished to distant parts of the globe, and in other cases the conditions suitable to their existence, and the means of their propagation are so well understood that their banishment is being systematically and successfully carried out, so much so that a disease such as small-pox, which at one time headed the list of fatal diseases, does not come in the category of anxieties of the mother of to-day; and pyæmia and puerperal fever, which twenty years ago were at timesdreaded scourgers in most hospitals, now occur only from culpable and punishable neglect.

A short study of these diseases should well repay us, showing as it will do that in by far the greater number of cases these severe constitutional derangements produce no effect upon the reproductive cells; that they are in fact incapable of producing a change that will be hereditarily transmitted. We shall learn, moreover, the part that they have played, and can play, in producing racial change by selection. The micro-organisms of disease are of many varieties, and each variety is capable of setting up its own peculiar disturbance. The disturbance set up by one kind we call small-pox, that arising from another kind, cholera, and so on. Now, the very curious point comes out that in most of these diseases, although the composition of the blood is profoundly altered, and many of the tissues undergo marked change, this change, fortunately for us, is quite of a temporary character, and when the attack is over there is only one test which will enable us to say that the body is not just in the same condition as it was before. This test is that it cannot be infected again for a long time, if at all, by the same micro-organism.

This induced immunity from further attacks hasreceived in the hands ofMetschnikoffa curious and very interesting explanation. He has shown that an army of small cells, called phagocytes, which wander through the blood and tissues, are able to attack the microbes of disease, and that after a struggle they are able in many cases to kill these voracious invaders. In so doing, however, the weaker phagocytes succumb to the struggle, while those which are left alive within the body of the convalescent patient possess the power of resisting and destroying the particular microbe which had undertaken the invasion. These resisting phagocytes, selected from the rest, together with their descendants, who share their resisting qualities, are able to prevent fresh inroads of the same enemy. We need not, therefore, assume that this acquired immunity, the sole relic of the attack, indicates any change in the ordinary muscle or brain cells of the body, or that the reproductive cells are in any way altered, for the immunity is due only to a change in the phagocytic army.

The germ cells in almost every case get off scot-free, and there is nothing in the organisation of a child to indicate whether or not his father or mother suffered from measles, or scarlet fever. It might at first sight be urged, in opposition to this fact, that, although we cannot recognise the child of a man who suffered from measles or scarlet fever by any visible sign, yet the child is in some way different, inasmuchas he is to some extent immune to those diseases. In favour of this belief, the many instances in which a fever has been brought to a country never before accessible to the germ (for instance, the introduction of measles and small-pox to newly discovered America, where fearful ravages were caused thereby), may be brought up as evidence to prove that those habitually living among the germs must have become immune and have transmitted this immunity to their progeny. Again, the black population of Sierra Leone have only a mortality of 24 percent.from malaria, while the mortality of the white settlers is 47 percent.;[12]and, in this case, it may be urged that the black race has become by transmission of immunity partially immune. But these cases which appear to be examples of transmitted immunity may receive another, and a much more simple, explanation. No two children of the same parents are alike in colour of hair, shape of limb, temperament,etc., and they also differ widely in their capacity to receive and combat infection. An epidemic of fever, therefore, will always select to kill those organically most liable to fall a prey to it, while the remnant, having by nature greater power of resistance, not only survive, but may also be calculated upon to produce progeny, on the whole, as resistant as they are themselves.

Races, therefore, subject to epidemics of a particular fever, suffer selections in the hands of the microbe of that particular fever, and those living are survivals cast in the most resisting mould. It may not be flattering to our national vanity to look upon Englishmen as the product of the selection of the micro-organisms of measles, scarlet fever, small-pox,etc., but the reasonableness of the conclusion seems to be forced upon us when we consider his immunity from these diseases as compared with that of natives of the interior of Africa, or of the wilds of America, whose races have never been so selected, and who, when attacked for the first time by these diseases, are ravaged almost to extermination. We find, then, that an ordinary attack of measles, scarlet fever, whooping cough, erysipelas, typhoid, or typhus fever, when it has passed away, leaves the tissues of the body in as sound and healthy a condition as before; and, indeed, were it not for this fact, the human race could hardly have existed at all, continually exposed as it has been, for countless ages, to the aggressions of these microbes. By exterminating these diseases, we shall, no doubt, preserve countless lives to the community, who will in their turn become race producers, but, inasmuch as the individuals thus preserved will inmany cases belong to the feebler and less resisting of the community, the race will not become more robust. In fact, it is probable that, as a race, we shall thereby suffer, for the banishment of the disease will enable the feebler members of the community to live, and in larger proportion contribute to the progeny of the future. That this is actually the case will shortly bepointed out.

But there are other microbes which, in addition to the production of blood changes, have a profound and lasting effect upon many of the tissues of the body. Such are the microbes of leprosy and syphilis.

The terrible ravages that the microbe of leprosy is capable of effecting are appreciated only by those who in Norway or elsewhere have visited those death-houses now fortunately to be found in but one or two parts of Europe. Yet, even in this case, strange to say, the germ cells do not seem to be reached by this loathsome disease, and it is not transmitted from parent tochild.[13]A disease of mediæval, not of modern, Europe, we need not discuss its action on racial change more than to say that, hideous as are its aspects, it must be looked upon as a friend to humanity; for, while the microbe of typhoid fever will attacka man who is healthy and living in healthy surroundings—excepting for the microbe that lurks in his well—the microbe of leprosy feeds upon those who are debilitated by conditions under which healthy and strong racial development is impossible. It is a depopulator of starved, ill-nourished districts, and the race recruits to its advantage from those more favourably placed.

In the case of syphilis, serious and often permanent tissue change is produced as a result of the action of the microbe, and in this disease, to an absolute certainty, an effect may be produced upon the offspring. Many suppose that this is due to the transmission of the specific microbe itself from the body of one or both of the parents to the developing egg. That such a thing is not impossible is shown in the case of silk-worm disease, in which the spores are to be found within the egg of the silk-worm moth. These spores subsequently develop and attack the tissues of the grub of the next generation. In syphilis the same kind of thing no doubt occurs; for a syphilitic child may subsequently infect the mother or nurse during the period of suckling. But there are other cases in this disease which appear hardly to be explained so easily, and we have to assume that the germinal cells are themselves changed in some way during their sojourn in the parental body, for after a certain time the disease is no longer capable of transmissionby the parent, and the children born after this period, though themselves diseased, are incapable of infecting those who tend them. We have every reason to believe, therefore, that there are no specific germs or microbes left in the body of the parent, and that we have to do solely with the more or less permanent change in the reproductive cells, produced by the microbes during their residence in the body of the parent. The children born during this period are frequently ill-nourished, possess recognisable indications of disease, and are subject to nervous and other affections.

We have here, therefore, for the first time, distinct evidence that an obviously acquired constitutional disease is transmitted, and that that transmission is in some cases due to a direct effect of the action of the microbe upon the germinal cells. The microbe of syphilis, unlike the microbe of leprosy, but like that of measles, feeds on healthy blood and tissue. It attacks the strong as well as the weak, and, if the weak more readily succumb, yet the strong and vigorous are more apt to acquire it. It is not, therefore, selective, like leprosy, and this fact, added to that of its capacity of transmission, ranks it as a disease distinctly inimical to race progress.

During recent years it has been discovered that the symptoms of phthisis and scrofula are due to a microbe, the tubercle bacillus. It appears, however, that this bacillus cannot gain access to, or multiply in, the tissues of a healthy and vigorous man or woman; most of us probably have often carried this micro-organism within the mouth or stomach, and though our gastric juice has not been able to destroy it, as is the case with so many of our invisible foes, it has been unable to pass into our blood or lacteals.Dr.Woodhead puts this factstrongly.[14]He says: “A perfectly healthy individual, placed under favourable conditions as regards food, fresh air, and exercise, is never attacked successfully by tubercle bacilli, the active, vigorous tissue cells being perfectly able to destroy any bacilli that make their way into the lungs, the pharynx, or the intestine.”

It appears, too, that a certain type of individual is readily attacked by this microbe, while the normal individual, debilitated though he may be by unfavourable external conditions, falls far less readily a victim. AsProf.Sir LauderBrunton[15]remarks: “We are constantly meeting with persons belongingto very consumptive families who escape the disease by living under conditions where the bacillus tuberculosus is likely to be absent. On the other hand, persons such as nurses are in all probability frequently inhaling the microbe, and yet are not attacked by the disease. In the first case immunity is probably due to the absence of the seed, notwithstanding the favourable condition of the soil; in the second it is due to the barrenness of the soil, notwithstanding the presence of the seed.”

Inasmuch as phthisis is markedly hereditary, we may look upon thetype, not the disease, as being transmitted. A phthisical type of person is one who comes of a family liable to fall a prey to this microbe, and he is recognisable by many distinctive characteristics of hair and complexion, and by qualities of temperament, feature, and figure.

Sufferers from phthisis are prone to other diseases, such as pulmonary and bronchial attacks, so that over and above the vulnerability to this one form of microbe they are to be looked upon as unsuited not only for the battle of life, but especially for parentage and for the multiplication of the conditions from which they themselves suffer.

The phthisical are attractive in personal appearance on account of their rich skin and hair colouring and their frequent brightness and vivacity, and their obvious delicacy also elicits a feeling of pity andwish to protect them. In consequence of this they easily marry, and they are as a rule very fertile.Galton[16]says: “There is fair doubt whether a group of young persons destined to die of consumption contribute considerably less to the future population than an equally large group who are destined to die of other diseases.” Now this phthisical type is very common with us indeed, and it appears to be an innate variation to which our race is liable. It is evident, therefore, that those people with the tuberculous variation who, even under the present circumstances, manage to contribute their quota to the population, would, were the bacillus tuberculosus altogether exterminated, contribute more than their share, and the type would become more common. And let it be remembered that this type, apart from the action of the bacillus, is a delicate and fragile one and liable to other affections, and the effect of giving the type any advantage in the struggle for life would surely imperil the well-being of the future of the race. When, some years ago, it was thought that a cure for phthisis had at last been obtained, great tribute was naturally and rightly paid to its discoverer; but had this cure proved as efficient as the more sanguine were led to expect, it would be terrible to contemplate the eventual suffering that would have resulted from the constantly increasingnumbers of the phthisical type that would have been born with each generation.

It is a hard saying, but none the less a true one, that the bacillus tuberculosus is a friend of the race, for it attacks no healthy man or woman, but only the feeble. It is like the bacillus of leprosy in this respect, but in this respect only, for leprosy attacks anyone living under certain unhygienic conditions. Remove these conditions—as we have done long ago—and the bacillus of leprosy disappears; its duties are over, like those of the extinct plants and fishes in the rocks.

The tubercle bacillus on the other hand attacks a type to be found not only in the poor, ill-fed, and ill-conditioned, but also those who live well. It is a disease of all classes, and those who live in well-ventilated rooms, and who conform to every sanitary regulation, may still belong to the type who fall a prey to it. It is certain, therefore, that, improve the external conditions of life how you will, this type will remain. It is also as certain that in giving the type a better chance than it has already, by preventing infection or by delaying the disease, the type will be more and more prevalent as each generation comes to life.

It comes out pretty clearly from our short study of the infective diseases that some of the microbes that cause these, such as the bacillus of tubercle, only feed on unhealthy human tissue, while the greater number of them kill, if anything, the weak rather than the strong. They are, therefore, on the whole, and as a natural consequence, our race friends rather than our foes, and if we attempt seriously to do away with their selective influence—viz., the elimination of the weak and the preservation of the strong—we must supply this selective influence by one equally potent, or the race will tend to deteriorate. What can be done in the future, and what it is expedient for us to do at the present time, will be more fully discussed in a subsequent chapter; but I may state at once thatpari passuwith our endeavour to prevent these diseases must be our efforts to enlist the co-operation of the human charity that would avert suffering in such selection as shall necessitate the birth of future generations from the healthiest and best of those amongst us. As selection is the race-changer, we must replace the selection of the microbe by the selection of human forethought.

A number of diseases, which are due probably to innate family predispositions, are known to us. Of these diabetes, hæmophilia, and some others are of comparative rarity, and may be left on one side inthis necessarily contracted sketch. Others, such as cancer and constitutional weakness of the respiratory and other organs, as well as insanity, are frequent enough to merit our close attention. Of cancer we at present know too little, and I propose to leave it on one side. Of inherited weakness of special systems we have many examples, such as a delicate respiratory or digestive mucous membrane, inherited variations in the mechanism of assimilation, and also gout and obesity—in fact, innate delicacy of all kinds, which renders their possessor less able to cope with his natural surroundings, let these be whatthey may.

There is hardly a family that can boast of the complete want of hereditary weakness, and among the children of particular families, where these weaknesses exist, some show the taint more than others. In times of hardship, cold, exposure, coarse food,etc., these weaker ones perish, and the race is consequently propagated from the stronger ones. Within certain limits cold, exposure and coarse food are compatible with great physical excellence, for the cold and exposure, hurtful to the sickly, braces and hardens the more robust, and coarse but nutritive food supplies him with energy and strengthens the powers of digestion. The finest races have been bred by hardship. It is proverbial to speak of “the hardy mountaineer,” and one cannot look at a lowland Scot without feeling that his stock had, in daysgone by and for many centuries, run the gauntlet of oatmeal porridge and cold east wind.

But we are rapidly diminishing those selective agencies which in the past have developed race vigour. As we shall presently see, skill in nurturing the sickly has, in modern times, wonderfully reduced the mortality amongst infants; improvements in methods of nursing, the replacement of cotton by flannel and wool, and the use of many foods, some of them artificially digested, gives a sickly infant a chance of living, and it survives its first most dangerous years. Then its chances are again improved, for the infective diseases are being held in check, and it has comparatively little to fear from them. Thus it survives and lives to adult age, when, like the hothouse plant, it is still protected from hardships to which the race had formerly been freely exposed. It lives to lower the average physique of the mothers or fathers who produce the next generation of children.

This increased preservation of the sickly has had the effect of increasing the life period of an average child, and this increase in the life probability is often and very rightly cited as an indication of the improved sanitary conditions of the people. Improved sanitary surroundings, as we have seen, are taken advantage of chiefly by the sickly, and thus with our increased probability of life we have diminishedthe average robustness of constitution, or innate healthiness of the race, for a larger proportion of sickly ones are living amongst us. In our day a greater number of parents suffer from phthisical, scrofulous and other taints than in days gone by, and these and other taints are passed on to their children.

So far we have seen what of necessity follows from our biological premises, but it is also possible, I think, to show by statistics that already very observable deterioration has taken place.

If we examine one of the reports of the Registrar General for births, deaths and marriages, we shall gain pretty full information concerning the deaths from disease, accident, old age,etc., that have occurred during the last thirty or forty years.

In Report 54, Table 17, the annual death-rates from various causes per million of population are given, and arranged in groups of five years from 1858 to 1890. We have there a history of thirty years, and even in that time a notable change in thishistory is to be observed. I have arranged the greater number of facts given in Table 17 in the following table, so as best to bring out those points which we are discussing. In the first group of disease are those due to micro-organisms, and a diminution of these diseases to a marked extent is to be observed of late years. Phthisis and scrofula placed by themselves in this group share in this decrease. In the second group are diseases that are due in great measure to carelessness, want of management, neglect and ignorance, such as convulsions, diseases of dentition, parturition and registered accidents. These, too, as one would expect, diminish yearly in a country where surrounding comforts and a sense of responsibility are on the increase. When we turn to the third group, that of constitutional disease, where the hereditary tendency comes in, we find an increase in almost all the hereditary diseases. A tendency to an increase of neurotic affections is shown by an increase in the deaths from nervous diseases, suicide and intemperance. A large increase in the diseases of the respiratory system is due in part to the increasing number of tuberculous patients who, kept from inroads of microbes, nevertheless readily fall a prey to other affections: there is, too, an increase in diseases of the circulatory system, in cancer, diabetes and other constitutional diseases.

Annual death-rates in England from various causes, per million persons living, in groups of years1858–1890—

[Version of the table for narrower screens]

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