I adduce this instance, for the sake of remarking respecting it, that on this subject also controversies exist, which must be settled by wider studies of the life of plants.
Cornaz has tried to derive from cows evidence in support of Thury’s theory. He had twenty-nine cows impregnated with attention to the rutting time, and from twenty-nine births received twenty-two females and seven males. Cornaz attested his experiment by a declaration, and the experiment was repeated in the French state domains.
But the experiment alone was striking enough to invite repetition. It also met with partial success. But the plan was afterwards entirely given up, perhaps in consequence of disappointments.
In this case it very likely happened—as in such experiments it very easily may happen—that, in consequence of insufficient practical knowledge on the part of the experimenter, the actual commencement of the rutting timewas overlooked. In addition, it is well known that animals, in consequence even of an amount of exercise not very exhausting, and in many other ways, as well as in consequence of the food they have taken, may exhibit variations in the activity of their rutting. It is not, therefore, surprising if the results of experiments show much that was unexpected.
I here pass over a great number of proofs which Thury gives in his essay. Funcke (1866) made in his ‘Physiology’ the following remarks on Thury’s theory:—“Although the origin and determination of sex is not indisputably proved to depend upon the degree of ripeness of the ovum, it appears to me that we have not reached the right time for determining the factor upon which it does depend. These experiments have been made to repose upon a fact, which fact certainly proves, beyond the possibility of dispute, a relation between the fertilization of the ovum and thesubsequent sex. This fact is that, in the case of certain creatures capable of parthenogenesis (unisexual procreation), we find that, from unfertilized ova one sex always results, and from fertilized ova the other. But any closer interpretation of this function of the semen is rendered nugatory in advance by this, that it is in some cases the male and in others the female that results from the unfertilized ova.”
Thury’s theory can be very suitably brought into agreement with the theory of cross-heredity of sex, and explained by the assistance of that view. The cow, at the beginning of her rutting, is not in a condition of great sexual vigor. If the ovum be effectually fertilized, it may be supposed that the bull, in procreative activity the superior consort, will be fitted not to reproduce his own sex, but that of the weaker cow. At the end of the rutting period the cow, which is broughtto the bull, has her ovum ripened to the highest possible degree, and in consequence, when compared, from a sexual point of view, with the bull, is distinctly the stronger and superior, and a male calf is in this case the result of conception.
According to the theory of cross-heredity of sex, female creatures should in the former instance be produced, and in the latter males, which same result is reached in accordance with the theory of Thury.
Attempts have been also made to apply Thury’s theory to the human species. The menstruation of women has been compared with the rutting of the lower animals, and has been considered a protracted, oft-repeated rutting. Now, as an ovum is specially developed every month, it follows that this ovum requires a certain part of a month to attain a more or less advanced degree of ripeness. According to this, the ova which are fertilized a short time after menstruationwill develop only female individuals, whilst those which have had a longer time in which to attain to ripeness would develop themselves into males.
The mucous membrane of the womb ought, about ten days before the beginning of menstruation, to thicken itself distinctly in consequence of a turgescence and dilatation of the vessels. In consequence it appears swollen and loosened, and it has reached the culminating point of swelling when the menstruation is at its highest. After menstruation the swelling does not immediately decrease, but lasts on for about nine days, until the mucous membrane returns to its normal condition. (Hensen.) Thus it seems that the swelling and hyperæmia in the womb appear at the same time as the conditions which lead to the ripening of the ovum. The fertilization of the human ovum would be, therefore, most efficacious at the time when the mucous membrane of the womb is also most appropriatelyprepared, and it is probable that the same moment is the one when all the other coincident factors are of a sort best calculated for the reception, the fixing, and the protection of the ovum. It is simultaneously with these processes in the mucous membrane of the womb, and in the other parts of the generative organs of the woman, that the ripening of the ovum is effected.
Now, it may appear not to be a matter of indifference (and may very likely even have some connection with the development of sex) whether the ovum is fertilized at a period during which the mucous membrane is passing through its changes in order to reach its highest point of swelling, or at the time, when, after menstruation, the mucous membrane is, during so considerable a period (nine days), passing through a retrograde metamorphosis in order to return to its normal condition. This protracted process seems to correspond to the protracted rutting in theform of a menstruation. If so, the human uterus, as Thury’s theory would declare, would be prepared, to a certain extent, in different ways, for the reception of the ovum, according to the different sex-conditions of the future child.
It is not sufficiently known to how great an extent the principles of Thury’s theory have hitherto found their right application to the case of man. They seem in practice to be applied in different ways.
It seems that in cases where a result was obtained it could be more easily explained by the principles which have been already described under the theory of cross-heredity of sex. The assumption of a greater or lesser degree of ripeness of the ovum which was to be developed was a very questionable one.
The different processes with which we have become, in more recent times, acquainted as symptoms of the ripening of theovum, are not here intended. Such symptoms can be observed both in the ova of the invertebrata and in those of the vertebrata. These symptoms, which are such as the attainment of the normal size of the ovum of the species in question, the protrusion of the orientation points (Richtungskörperchen), the steps towards the formation of a female anterior nucleus (Vorkern), etc., do not here apply, for the recognition of that higher degree of ripeness in the ovum which is necessary at the time of fructification for the development of a male individual.
All the above symptoms occur alike in the ova destined for the male and for the female sex. That ripeness of the ovum upon which Thury’s theory insists, lies in the nature of the ovum apart from any anatomical signs. It is a condition of the ovum which we can only attempt to explain by laying down the principle that an ovum which has been for a longer time prepared in the female generativeorgans previously to its fertilization, must be riper than another which has had less time for this preliminary process.
We have mentioned above that on the occasion of Thury’s experiment, the desired result was effected in twenty-nine cases. Pagenstecher, Siebold, and Köll have dealt critically with Thury’s work. Coste was not in a position to confirm these experiments, nor to verify them. In order to test Thury’s results as applied to the human subject, Schröder obtained the assistance of young women, who were in a position to give him positive and accurate information respecting the time at which they became pregnant. The women could name the day on which they had had sexual intercourse, and knew the date of the last menses. From careful calculation of the interval between these dates, it was possible to ascertain approximatelyat what stage impregnation of the ova took place, the degree of ripeness of the impregnated ova could also be inferred from the space of time that had elapsed since the last menstruation, and the sex of the fœtus was noted. Schröder found that on an average of twenty-six cases in which boys were born, the conception had taken place 10.08 days after menstruation; on an average of twenty-nine cases in which girls were born, 9.76 days after. In consequence, he was not able to confirm Thury’s theory in the case of the human subject.
The experiments of Albini in Naples (according to Kronecker’s report ‘Centralblatt für medicinische Wissenschaft,’ 1868), which he made during four years in his great poultry-yard showed in the first place that hens for eight days after being separated from the cock laid none but fertile eggs. On the ninth and tenth day the fertile and infertileeggs were of equal number. On the twelfth day all the eggs were infertile. Nevertheless fertile eggs appeared even on the eighteenth day. It is possible that they had been impregnated by spermatozoa which had remained in the folds of the mucous membrane of the uterus.
Hens never yet impregnated, or such as had not been impregnated for at least a month, in three days (after impregnation) laid fertile eggs, which increased in number daily.
According to Albini, hens can in Naples leave the eggs which they are hatching. The shell can be partly broken off and again replaced without the embryos necessarily perishing. But care must be taken that no fungoid growth reaches the germ, as this is easily fatal to it. Indeed, it has been recently shown that new-laid or well-preserved eggs are free from all micro-organisms. When these appear they havemade their way into the egg through the mechanically injured or otherwise altered calcareous shell. They do not have their origin in the egg from the mother. The egg of the bird is perfectly free from micro-organisms when it is laid. If, however, only traces of pure cultivations of micro-organisms be in a suitable way applied to such eggs externally (Lenderer), they always have a fatal effect upon the developing germ, even when they are not any of the so-called pathogenic microbes.
And now the result of Albini’s breeding experiments upon poultry with respect to the origin of sex.
From three to six days after intercourse with the cock the hens lay eggs, from which on the average an equal number of males and females are developed. In the warmer part of the year the number of males appears to be greater.
Better nourishment of parents seems also to exercise an influence over the sex of the young.
Such eggs as were laid from ten to fifteen days after complete separation from the cock, gave when hatched generally a distinctly greater number of females. Albini found that the greater number of these died of anæmia. He ascribed that to imperfect fertilization, and considered that development of an excessive number of females was to be ascribed to the same cause.
Albini inclines towards the theory of Thury, in accordance with which the principal cause of the development of sex lies in the degree of ripeness of the ovum. He is opposed to the theory of Coste and Gerbe, which declares that the ova of the birds and mammals are fertilized when they fall from the ovary. The place where this took place was, according to their theory, exactly localized, at the opening of the Fallopian tube, and not at any place in the length of the tube.
Fertilization in the Fallopian tube or uterus is allowed to be possible, and it is admitted that, in exceptional cases, fertilization of the hen’s egg is possible so long as it is not surrounded by the shell-membrane.
This opinion, however, is in direct contradiction to that of Lenkart and Newport and many others, who hold that the albumen, which gathers around the yolk in the oviduct, hinders the penetration of the spermatozoa into the yolk. When Albini had collected his facts he came to the conclusion that, in the case of animals which bear many young, the last are mostly male, and explains this by the hypothesis that the ova passing through the Fallopian tube thrust the semen back, so that the ova which come behind are therefore fertilized in a more advanced stage.
Meyer believes that he has incontestably proved against Ahlfeld that the sex is determined at conception. He does not appear tobe disposed to admit the existence of male and female ova in the ovary; but he thinks it absolutely certain that the sex is determined at conception by the reciprocal action of the ovum and the semen. This view follows from the fact that, as Thury’s theory demands, a fertilization and a determination of the sex must necessarily take place as regards time either at the beginning or the end of the mingling of semen and ovum.
The longer the ovum exists free from the ovary, the longer it remains without the surrounding of those elements (contained in the ovary) which are necessary to it. Apparently, in consequence of the absence of these elements, it is all the time drawing nearer extinction, or it may at least become gradually less capable of maintaining its own sex—which is feminine. At least, it appears, before it is overtaken by the total extinction which threatens it if it is not fertilized, to lose the energy necessary, when fertilizationensues, to maintain its sex, and so may become fitted to assume the opposite masculine sex. This much, however, seems to be quite certain, according to Mayerhofer, that the human ovary does not contain male and female ova already possessed of sex. Equally impossible is it to imagine male and female seminal filaments (spermatozoa) already existing in the organism, and provided with distinct capacities for generating definite sexes. We are unacquainted with any special anatomical signs indicating any such distinction, and do not, even after microscopic investigation, find ourselves prompted to assume the existence of such distinct forms as would allow us to conclude the existence of so fundamental a difference. It is true that in many of the lower animals different forms of spermatozoa are known. These are developed in one and the same testicle, and under the microscope whisk about confusedly with vivacious movements. We find this in the caseof a kind of snail (Murex brandaris). If we observe a drop of the semen of this creature diluted with sea water, the greater number of the spermatozoa, possessing head, central portion, and tail, move about very energetically. Amongst them are other spermatozoa, distinctly larger and of different form, whose shape suggests spindle-like elements, ending in thin thread-like tails. All these objects exhibit a striking vivacity of movement. Whether these objects represent a particular kind of spermatozoa (as some have supposed), exhibiting definite sexual character, or whether they are not cells, striking on account of their movements, out of which spermatozoa are developed (the so-called spermatides or spermatogonia, transition forms out of which spermatozoa are developed), is at present an open question.
H. A. Pagenstecher attempted an important readjustment of Thury’s theory, and tried to show that it might be made concordant withwhat had been elucidated by previous observations. He holds fast to the axiom (Joh. Muller, Home, Geoffrey St. Hilaire, etc.), that the embryo is at first sexless, and that the ovum after its fertilization still has this character, and must possess the potentiality of developing its sex in two different directions. The factors which determine sex must be external to the embryo.
Pagenstecher remarks that the relations which have existed anterior to the fertilization of the ovum, as well as its age (with which its ripeness is connected), are from the outset without influence on sex.
The embryonal germ, before its fertilization, is an embryo whose sexual development is undetermined. In this case fertilization acts as an external factor in the direction of determining the sexual quality of this indeterminate embryo.
The act of impregnation would be of influence upon the sex of the embryo in accordancewith the character of the father. That follows from Pagenstecher’s explanations of Hofacker’s observations. According to Hofacker we get from men of twenty-four years of age and upwards, as also from sheep of a certain age, an average of a greater number of males. In the case of mothers, also, as we have already pointed out, the sexually-stronger age (Lenkart, Girou de Buzareingues, Hofacker, Morel de Vindé, Sadler) and the food have an influence upon the majority of births of female individuals. Here should be added the experience of Nasse and Van den Bosch. The observations of Dzierzon, von Siebold, Lenkart, and von Berlepsh, on the development of sex in bees, and, according to von Siebold, among the Psychids, should also be taken into consideration. When the females of certain Psychids are not impregnated they lay only female ova. If they are impregnated, male ova appear also. The tree-lice (Cestoni, Réaumur) give birth to living youngwithout impregnation. These are at first only female,afterwards males appear as well. After this impregnation commences, and the females begin to lay ova.
The experiments of Knight, who found that melons and cucumbers produce male blossoms under higher temperature and female under lower (which was verified by Mauz), demonstrate that, in this case, such external factors as warmth, light, dryness, have an influence upon sex. Pagenstecher, however, believes that the conditions of origin of sex are not the same in animals and plants. We must not, he says, from these observations draw conclusions off-hand respecting the sexual propagation of plants nor of animals in general.
It must be further pointed out with regard to the thesis that ova which are emitted last have had more time to ripen, that we must reflect whether the process of ripening may not have also begun late.
Thury’s observation that the last egg laid by a singing bird developed a male (communicated by O. Bourrit), and that in the case of hens the majority of the later eggs were males, seemed to Pagenstecher not quite certain. He mentions also a method by which, in poultry breeding, the breeding experiments can be conducted on a regular principle, which I shall quote word for word:—
“For this experiment a number of hens are taken which may be anticipated to be “setters,” unless the use of incubators is preferred. The hens are to be separated, and the eggs which each one lays in her own particular nest are to be marked with numbers corresponding to the days on which they were laid.
“The eggs of the different hens are now to be rearranged, so that the eggs which each particular hen is given to hatch shall, as nearly as possible, have the same numbers. For example, if the number of the hens be six, and the period of laying up to the timewhen the hens begin to set be thirty days, one hen will have eggs to hatch with the numbers 1 to 5, the next 6 to 10, the third 11 to 15, the fourth 16 to 20, the fifth 21 to 25, the sixth 26 to 30.
“In this way the doubt will be avoided, which necessarily arises, if I give the eggs of one hen, although marked, to be hatched by her alone.
“In the latter case, it can very seldom be known with certainty from which egg-shell a cock or hen issued.
“In this experiment, on the contrary, one can quietly wait until the cocks and hens in the growing broods of the different hens can be clearly distinguished and numbered, seeing that each brood has numbers (of the days of laying) of very nearly the same value. The experiment is easier and less subject to the possibility of error when the eggs belong to different varieties and are taken from known parents.”
Fertilization in many cases alters the future sex as soon as it affects the germ in some corresponding manner. The germ develops itself, and, in the case of creatures whose ova develop without fertilization, evolves one, or the other, or both of the sexes. According to Pagenstecher, fertilization often alters the determination of the sex of the germs which attain to development in the ova. The point of time in the life of an ovum, at which it has reached that degree of ripeness which gives it such a character that the semen can no longer affect the determination of the sex, cannot be absolutely settled. A more powerful bull might beget female calves earlier in the late rutting time than an older one.
After further explanations and critical expositions, which suggest themselves in the course of the examination of the theory, Pagenstecher lays stress upon the following important dicta of Thury’s teaching:—
1. Sex depends upon the ripeness of the ovum at the time of fertilization.
2. The ovum which, at the moment of fertilization, has not yet reached a certain degree of ripeness, produces a female. If this degree of ripeness has been passed, the ovum, upon fertilization, produces a male.
3. If at the time of rutting a single ovum is detached from the ovary, and descends slowly through the genital canal (animals which bear a single offspring), fertilization taking place at the beginning of the rutting suffices to produce a female, and at the end of the rutting to produce a male, provided that the change in the condition of the ovum takes place normally during its passage through the genital canal.
Both the theory as Thury stated it, and the critical remarks that have been made upon it, have been further elucidated in many subsequent works. Here Pictet, Chavannes, C. Vogt, De Philippi, and others, have takenpart. Pictet believes in the uniformity of the sexual life of vegetables and animals, so that both would be subject to identical fundamental laws.
The facts which stand in certain relations with the fundamental laws are numerous, and the manner in which they tend to affect those fundamental laws occasions various combinations in the variety of phenomena.
For the animal kingdom Thury adduces a number of observations as the foundation of his teaching. We shall here turn our attention to some of them.
We have already pointed out that in the case of the eggs of the singing birds, which are laid by turns, the young which emerges from the last strikingly smaller egg, the so-called “nest egg,” is always a male.
According to the theory of Thury, the ripeness of the ovum depends also upon the place which, in the animals, it occupies in the ovary. In consequence, according to thisauthor, it is not improbable that we shall find an irregularity in the successive production of male and female ova.
If the activity of the generative apparatus of the female should be increased by any circumstance, in the case of the animals the ripening of the ovum would be accelerated. The consequence would be an earlier detachment or emptying out of the ova from the ovary. In consequence, the generative operations in the animal are of a more complex nature than in plants, a fact which is of great significance for the determination of sex.
The continuous intercourse of the male with the female increases the capacity for accelerating the ripening of the ovum. According to Burdach the mother animals who do not have frequent intercourse with the male bear more females, because their ova do not, before fertilization, attain so high a degree of ripeness as to be able to develop into males. Also, it appears from observations onanimals, not to be improbable that the male chooses the time of intercourse. The determination of the chosen time depends upon many influences. The causes of choice may be sought in many factors. Some of these depend upon external influences; others have internal causes. The causes may be general or personal. They may depend upon external form, or be occasioned by other phenomena of the animal world. It is always easy for these phenomena, which in their nature are of the most different kinds, to escape observation.
Amongst cattle and sheep the first-born are more often females. (Girou.) Also in the human species a greater number of females are observed amongst the first-born. Here, on the one hand, regular intercourse with the male is to some extent unfamiliar; whilst, also, according to Thury, the choice of the date of marriage might be of importance. The constancy of the births may be explained by theregularity of the intercourse of the two parents in consequence of the reciprocal ties which surround family life.
From illegitimate births more girls result than from marriage. The reason of this might be sought in the influence of the active excitement of the female at the time at which the conception took place, that is, shortly after menstruation, when the woman is most easily excitable.
The various theories respecting the explanation of the production of sex which are known to us, from the earliest accounts down to the modern predominance of natural philosophy, have been collected by W. His. (‘Archiv für Anthropologie,’ Band 4, 5.)
Since then, it is true, during the course of successive studies, and more especially of those which have been made during the present century, many substantial alterations have appeared in the views held respecting thecause of the different development of sex. We have seen this above.
Thus, discoveries have been made which have exercised a very wide influence, for example, that of the ovum in man and in the other mammalia (Baer, 1828), or the penetration of the spermatozoa into the protoplasm of the ovum as a necessary condition of fertilization. In later times it has been made certain that the head of the spermatozoon is a nucleus, and that only one spermatozoon penetrates into the interior of the ovum. Afterwards its head as a nucleus unites with a nucleus-part of the ovum, forming a new nucleus in the ovule, which, together with the surrounding protoplasm, serves as the point of departure of the further processes of development, and in this condition is described as an oosperm. After this follow other extensive details of the process of development, which will not be described here. It may be already seen,from the few principal factors of the process mentioned, that our theory respecting the development of the sex in the embryo will have to be substantially altered. We shall here adduce only the fundamental doctrines respecting the development of the generative organs laid down by Waldeyer in his masterly work on the ovary and the ovum. The teaching for which we are indebted to His, Kölliker, Schäfer-Korschelt, Heider, Duval, Kollmann, Minot, Bonnet, Bergh, Prénant, Balfour, Romiti, Kuppfer, and others, must also be well remembered, as well as the acquisitions of new information connected with the physiology of the embryo, and, of quite recent date, the mechanism of development (Roux), which can acquaint us more especially with the particulars respecting the states and processes in the ovule during the earliest life-stages of its development.
The doctrines of the physiology of metabolism in men and beasts under differentcircumstances have exercised so powerful an influence over our comprehension of the relations of the individual during the sexual-life, that we practically find in all these teachings a powerful support, whence we may obtain many elucidations bearing upon the question lying before us, and may discover the principles necessary to complete our theory.
But, before entering upon the fundamental principles of the theory which I have set forth, I wish to mention a treatise of Mayrhofer’s, the principal results of which I shall briefly recapitulate. After that I shall mention briefly such information as I have met with respecting the nutrition of the mother.
Mayrhofer was led by critical notices and the observations of others, and, further, by his own experiences, to conclusions which he set forth in propositions, some of which I select here.
In the plants and the lower animals foodplays a principal part in the development of sex. The sex is not generated, but depends upon external influences over the fruit which is in a state of development. And here we have a stage which precedes the separate sex in man, in which stage sexual neutrality must be regarded as normal, where also we find a kind of hermaphroditism.
Whether sex in the human species is determined at conception, or only develops itself afterwards, we must attempt to discover from obstetric experience.
The twins and triplets contained by one chorion are of the same sex, and have a common placenta in which the blood passages of both umbilical cords communicate with one another. On this account, also, many opine that the identity of sex is occasioned by the intermixture of the blood, an opinion regarded, on the contrary, by others, with incredulity, because the intermixture of the blood might very possibly lead merely to a mixture andnot to homogeneity, under which circumstances dissimilarity of development would be possible enough. We may here adduce the following facts also (Jhering): The armadilloes produce a number of young in one litter, which are normally developed in a single chorion, and are of the same sex, as in the case with man when twins are developed in one chorion.
Heartless monstrosities (Acardiaci) are, in spite of imperfect nutrition (the conditions of proper nutrition by the blood are wanting in the embryo), of the same sex as normal offspring. Now, cases of this kind demonstrate that, in the later periods of development, although the conditions of nutrition are not alike, nevertheless the similarity of sex in the twins is maintained; so the foundation of the future sex would be laid at the period of conception. This rule which proves valid for the twins found in a single chorion, would apply for all human ova in general, becauseall possess the capacity of attaining their sexual character at conception.
According to Mayrhofer, placentæ are rare in which, where there are two chorions, communication is found between the vessels of the two umbilical cords. In addition to what has been already mentioned, Mayrhofer lays down the law, which we find frequently stated in many quarters, that the older of the two parents has a greater preponderance in favor of the propagation of his, or her, sex. Especially the physical maturity on the man’s side enables him to propagate his own sex, either in connection with younger or older women. A superiority on the part of the woman produces girls.
Our author only partly supports Thury’s theory, and considers it an open question whether the time of impregnation has any influence on the origin of sex. But he lays down this principle, that an economy of the semen by infrequent indulgence inintercourse is extremely favorable to the production of males.
It may be possible to obtain more exact data respecting the origin of sex from the artificial breeding of fish. In this case the properties of the sperm, as well as of the ova, might be observed at an earlier date by means of a fertilization effected externally. Attention might be also paid to the age of the parents. In short, all the factors of artificial influence upon the development of sex can in this case be taken in hand and controlled by varying the process of artificial fertilization. The author does not appear to know that the results obtained by artificial breeding differ remarkably from those which are the consequence of the natural multiplication of fish, nor that the development of sex is unfavorably affected in many ways. The cause of that lies very likely in the nutrition of the young fry, and perhaps, also, partly in cross-breeding.
What influence the physical welfare of the parents, and especially of the mother, has on the sex of the offspring in man, besides other factors deserving of attention, ought to be discoverable from the statistics of the lying-in hospitals. This is, in my opinion, hardly to be expected.
On various occasions, whilst taking into consideration the possibility of an influence on the part of the parents over the sex of the child (in such respects as have been placed before us in the literature dealing with this subject), we often had occasion to direct attention to the food of the parents. And especially the food of the mother seemed to us to be of the highest importance.
Now, it is universally known that metabolism is increased during pregnancy. The products of excretion in the case of pregnant women are much smaller than the quantity of matter taken in, in the shape of food.The difference, to a great extent, represents the matter taken to form the bodily substance of the embryo, in accordance with the anterior laws which have been fixed by the doctrines of the physiology of metabolism. It will, then, be necessary to pay particular attention to the investigation of metabolism. Suggestions are not wanting. They will be found amongst the observations of leading specialists. For example, Winckel observed that during pregnancy the temperature was slightly raised. This increase of temperature must practically be explained as due to the higher and more productive process of oxidization, which has to be accomplished by the human female for the sake of nourishing the fœtus.
During pregnancy the number of blood corpuscles suffers an observable diminution. Still plainer is the reduction of the quantity of hæmoglobin, when measured with Fleischl’s hæmatometer. This last phenomenon is verylikely connected with a greater consumption of hæmoglobin, the substance being used up by oxidization.
Observations of setting hens are not without interest. In their case, also, a diminution of hæmoglobin is observable during the period of incubation. The hæmoglobin can sink to nearly 50 per cent. of the normal amount. With the increase of hæmoglobin in the embryo and its simultaneous diminution in the mother during incubation, it happens, at a certain period in the process of development, that the embryo in the egg and the setting hen possess a nearly equal measure of hæmoglobin with a nearly equal number of blood corpuscles. An increase of the quantity of hæmoglobin until the normal amount is reached may be observed in both towards the end of incubation.
The Rhine salmon each year go up in a well-nourished condition from the sea into the fresh-water streams to spawn. Therethey remain several months. They lose much of their muscular substance. (Miescher.) On the other hand, a great development of the sexual organs and of sexual secretions takes place, produced, probably, at the expense of the used-up muscular substance.
Many have paid particular attention to the nourishment of the maternal organism. Investigations have also been published dealing with the nutrition of the parent animals in cases when it was desired to exercise an influence over the sex.
In fact, we have frequently touched upon such subjects, although only lightly. Here, as we are about to proceed to the subjects of nutrition and metabolism in the human female awaiting impregnation, we find ourselves compelled to acquaint the reader with a number of facts which permit us to assume a connection between the food supply (including metabolism) and the development of sex.