Chapter VII.ETIOLOGY.
There is hardly anything on earth, or between it and heaven, which has not been regarded as the cause of Leprosy; and this is but natural since the less one knows, the more actively does his imagination work. And since all that was known of Leprosy was that it was a loathsome disease, search was made everywhere for a cause. We will not linger over the older literature of Leprosy. That may be found fully dealt with in Danielssen and Boeck’sTraité de la Spedalskhedand in Hirsch’sGeographical Pathology.
Only after the work of Danielssen and Boeck can one say that Leprosy entered the ranks of the scientifically investigated diseases. At that time, in 1840, when they commenced their investigations, Humoral Pathology held the field. Most diseases were ascribed to changes in the blood, and they therefore endeavoured to establish that there was in lepers a change in the blood which they regarded as the cause of the disease symptoms, especially the node formation. These changes in the blood they believed were caused by unfavourable conditions of living, and as theywere not able to find any convincing evidence of the power of infection of the disease but several of its limitations to certain families, they drew the conclusion that Lepra, as they called it, might appear spontaneously, that is to say, that the sanguineous dyscrasia which led to leprosy could be developed under unfavourable conditions of life, but that it was in most cases hereditary. It must, however, be noted that Danielssen always regarded Leprosy as a specific disease, described it as such, and sought for a specific cause, and the fact that he did not find it must be ascribed to the circumstance that microscopical technique and microscopical aids, especially the immersion lens, were at that time either insufficiently developed, or not yet discovered. The teaching of Danielssen and Boeck was everywhere adopted, especially their view of the heredity of the disease. The fish diet and damp cold theories are only attempts to explain the so-called spontaneous development of the disease, and they are founded on the fact that Leprosy is chiefly present in littoral districts and on islands.
Of other Norwegian investigators, the late Dr. Hjorth held the view that Leprosy could not be ascribed to a specific cause, and that it was certainly not hereditary. Dr. Holmsen regarded it as a specific miasmatic and non-hereditary disease, and finally Prof. Lochmann stated that it wasspecific, contagious, and hereditary. While Danielssen and Boeck always required a leprous ancestor in order to recognise a case as hereditary, and when this was not forthcoming, found in the presence of the disease in other branches of the family, proof of its heredity, Biedenkap, as he was unable in many of his cases to determine the existence of leprous ancestors, widened the definition of heredity by assuming that unfavourable conditions of life might produce in the organism conditions which became hereditary, and showed themselves in later generations as leprosy. In the year 1869, Dr. Drognat-Landré published a book with the title,De la contagion seule cause de la propagation de la lépre, in which he sought to prove that heredity had nothing to do with the spread of Leprosy. That is, according to our view, the right standpoint, as we shall endeavour to demonstrate.
As is seen from the above short summary of the views of Norwegian investigators, some maintain the non-specific origin and heredity of the disease; one only, the non-specific origin; one a specific cause and no heredity; and finally, one a specific cause, contagiousness and heredity.
It is rather remarkable that supporters both of the specific and the non-specific origin of the disease should regard it as hereditary. It apparently struck none of them that possibly thespecificity of a disease, that is, its development through the action of a poison, might be incompatible with heredity. Since the discovery of the Lepra bacillus and its recognition in all leprous products, it is now everywhere admitted that it is the cause of the disease, and it would therefore be superfluous to indicate which of all the symptoms of the disease point to its specific nature. All this was shown in a communication made by one of us to the Copenhagen Congress in 1884. We start then from the assumption that Leprosy is a disease caused by the Lepra bacillus, although it is as yet not strictly scientifically proved, since inoculation on man and animals has not been definitely successful.
The question as to heredity now is, Can the lepra bacillus be conveyed by heredity. This is Baumgarten’s view; he holds that both Tuberculosis and Leprosy are thus spread, that the bacilli of both diseases may be transferred to the children and there remain dormant, but that they can thence be conveyed to another generation, and from it to a fourth, fifth, etc. generation, and then in the third, fourth, etc. generation become once more active and cause the disease. We see at once that this is only a modification of Biedenkap’s heredity, a peculiarity of the organism which finally becomes evident as Leprosy. In place of his undiscovered peculiarity, we have undiscoveredlatent bacilli. Baumgarten’s view is therefore only a hypothesis for the explanation of the origin of the two diseases. The hypothesis may be tested from two points of view: first, we may sift it theoretically; and secondly, we may investigate whether it can explain the distribution of the disease.
We must first endeavour to make clearwhat heredity is. As a matter of fact we do not know; we are familiar only with a series of phenomena which we call heredity, just as we have a series of phenomena which we ascribe to the force of gravity, without knowing what gravity or its force actually is. If we consider only the phenomena of heredity, which are nowhere so completely and clearly put together as in Darwin’s works, we find that he presents so-called laws of heredity, that is, he has noted the most frequent phenomena of heredity, and thence deduced a law. If the phenomena in the conveyance of a disease to one’s descendants are to be called heredity, they must correspond with the rest of the phenomena of heredity. And looked at thus, we know of no specific disease which can be called hereditary. The conditions which are hereditary are all anatomical and physiological peculiarities of the organism. A bacillus which is living in the organism cannot be regarded as one of its anatomical or physiological peculiarities; it is a parasite. Now it is beyond doubt that parasitesmay be conveyed from parents to children. Such are theAchorion Schönleini, and theAcarus Scabiei. But this is no hereditary communication, it is simply a present from the parent to his child. But, it is objected, if the parasite is conveyed through the organs of generation during copulation, then it is no longer a present or an inoculation, it becomes hereditary. This appears to us a remarkable argument, that conveyance by means of the organs of generation can change the nature of the parasite and convert it into an anatomical constituent of the organism of parent or child. A parasite remains always a parasite, and since its conveyance from one adult to another is called infection, we cannot comprehend why its conveyance to an ovum or a fœtus should be indicated by another name. Were Baumgarten’s hypothesis correct, it should certainly be called a hypothesis of latent infection, and not a hypothesis of heredity. We said above that we knew of no specific disease which was hereditary. To this it will naturally be objected that syphilis is a typically hereditary disease. But we reply that syphilis is a disease communicable to children, but that it is not hereditary, and in order to maintain this statement we only need to place in parallel the phenomena of the conveyance of hereditary peculiarities and those of the communication of syphilis to children, in orderto make it perfectly clear how different the two methods are.
Anyone who will maintain that these two forms of conveyance are the same, and both hereditary, must evidently sacrifice facts.
We hold then, that a specific disease may be conveyed to the children, but that it is never hereditary; the communication is by infection.
And since we regard leprosy as a specific disease we hold that it cannot be hereditary. There remains, however, the further question whether it can be conveyed to descendants by latent germinative infection. This cannota prioribe denied, although we have no right to assume it from our knowledge of the lepra bacillus and ofthe occurrence of the disease. We have indeed sought above to point out the possibility that the lepra bacillus is attenuated in the maculo-anæsthetic form of the disease; but we know of no phenomenon which would allow us to assume that the bacillus could occasionally become quite innocuous, and call forthnosymptoms of disease.
All this, however, proves nothing against the hypothesis; and it is always a dangerous thing to use a simple absence of knowledge either to contradict or to found a hypothesis.
But we think we can supply an almost incontrovertible proof that Baumgarten’s hypothesis is wrong. It is well known that the Belgian Father Damien became a leper in the Sandwich islands. If the Father was of pure Belgian ancestry, and his disease was caused by latent hereditary bacilli, then these bacilli must have been at least several hundred years old, unless one assumes that one of his nearer ancestors had had connection with a leper, and that in this way the Father had acquired his bacilli. Against this is the explanation that the Father who tended the lepers on Molokai, with self-sacrificing love, was, through some want of care or caution, infected as he went in and out among the lepers. The choice between the two explanations does not appear to us a difficult one.
The view of the non-communication of leprosyby latent bacilli is further strengthened by the fact that there are places in Norway where many descendants of lepers live without one single one of them becoming leprous, as for example, in the town of Bergen where the descendants of lepers may certainly be numbered by thousands; and further, we have demonstrated by our investigations in North America, that of the numerous descendants of Norwegian lepers there, not one has developed the disease. But since about one hundred and seventy leprous Norwegians have emigrated to America, it may possibly be that the disease is spread by infection. There are indeed cases in America which have possibly arisen from infection, but they are not sufficiently definite to serve as arguments for its contagion. But even if leprosy be a contagious disease, one can easily understand how it should spread little, or not at all, in North America, when one compares the social condition and especially the cleanliness there with that in Norway, and probably especially with that of the districts in which leprosy is most prevalent. In North America the dwelling houses are roomy, so that the lepers whom we saw there had usually their own room, or at least their own bed; and everywhere, even among the Norwegians, great cleanliness is observed. And this is, according to our view, sufficient isolationin order, in most cases, to prevent the spread of the disease.
That leprosy is really contagious is primarily evident from its nature as a bacillary disease. No one has been able to demonstrate the presence of the bacillus outside the human body, so that we may abandon the idea of a miasmatic origin.
Unfortunately, all attempts to inoculate animals have failed. The now old experiments of Neisser and Damsch, as well as our own, we may pass over. We dealt with them in our Copenhagen communication. Since then Melcher and Ortmann believe that they have communicated the disease to rabbits. Dr. Ortmann has kindly sent us preparations from the infected rabbits, and on close examination of them we regret to say that we lost our faith in the leprous nature of this affection of rabbits. We found both caseous degeneration and myelo-plaques in the preparation, which, as we have noted, we have never found in leprosy. At the same time the affection does not look exactly like tubercle, and it is possible that in rabbits leprosy appears otherwise than in man. But we may note that Veterinary Surgeon Nielsen has, here in Bergen, observed a disease in mice, which shows a close resemblance to Ortmann’s rabbit leprosy. Inoculated on a rabbit, the disease appeared with new growths in the cœcum, justlike Ortmann’s rabbit leprosy. These new growths had certainly more resemblance to tuberculosis; but there were in them, at many places around the vessels, cells, crammed full of bacilli. Nielsen’s investigations are not yet concluded, but it is possible that the disease is one of animals as yet unknown, which Melcher and Ortmann have by chance conveyed to their rabbits. All the inoculations of leprosy on rabbits which Dr. P. F. Holst made in the laboratory of the Lungegaards Hospital were unsuccessful; not one of the infected animals became leprous.
Although, as we have stated above, the lepra bacillus has never been found outside the human body, this might possibly be dependent on insufficient search, and it might be possible that the old view at present maintained by Hutchinson is the right one, viz., that leprosy is caused by the eating of putrifying fish, or that the contention of Holmsen that leprosy is a miasmatic disease, is correct.
Against Hutchinson’s hypothesis there is in the first place the fact that we have never succeeded in cultivating the bacillus, which, if the bacillus lived as a saprophyte on decaying fish, would be a very simple matter. And there are, secondly, places where the inhabitants certainly and frequently enjoy decaying fish without the disease appearing. And thirdly, there are many placesauthoritatively indicated where leprosy is present, and where no fish is ever eaten. For his hypothesis of the miasmatic origin, Holmsen can only bring forward the fact that the disease is often limited to certain districts. This is certainly correct, but this endemic appearance of leprosy may be as readily explained by infection, while the localities affected do not give the slightest support to the assumption of a miasma. Such areas are found here in Norway, both on the bare cliffs, on the coast, in the valleys, and on the mountains.
There is, therefore, no other course open to us but to assume the infectiousness of the disease, and thus the spread of leprosy is readily understood; while by the assumption of heredity, or Baumgarten’s latent germinative infection, it remains absolutely inexplicable. These two last causes are to our thinking absolutely proved to be non-existent by the case of Father Damien; by the results of our investigations in North America; and by the diminution of the disease in the descendants of lepers in the Norwegian towns.
Butdirect proofsof its contagiousness may also be obtained. Such are given by Drognat-Landré in his book, and also by many other observers. Norway can supply many proofs; but against these it can always be urged that it is impossible to exclude the possibility of inheritance on account of the widespread nature of thedisease. But we think we can supply from Norway a still better proof in the shape of the gradual diminution of the disease during the last thirty-five to forty years.
Up to 1856 leprosy probably increased in Norway; we cannot speak more definitely, as previous to that year there was no exact or sufficient enumeration of the lepers. But we have grounds for believing that we have obtained, by means of the yearly census begun in 1856, a pretty exact knowledge of the number of new cases in the years 1851-55, and this shows that the number is considerable, and almost exactly corresponds with the number of new cases in the next five years, 1856-60. This, we think, indicates that the total number of lepers in the two quinquenniums was pretty much the same. Now we know that there were in Norway in 1856 over 2800 lepers. The number was estimated in 1836 at 659, and in 1845 at 1122. According to this estimate a considerable increase had taken place. We can, however, with certainty say that the numbers for 1836 and 1845 are too low. In the first place, the enumeration was not undertaken by medical men, and secondly, even now, there are many lepers overlooked at every enumeration, or, to speak more correctly, they are not discovered because the patients conceal their condition. But that the number of those overlooked in theyears 1836 and 1845 can have been so great as the difference between the numbers for those years and that for 1856 is scarcely credible, and it therefore appears probable that the number of lepers in Norway increased during the first half of the century.
In the year 1856 the first Leper Asylum was opened in Bergen. Previously to this we had in Bergen the St. Georg and Lungegaard’s Hospitals, which together served for 200 patients. In Molde there was also a small hospital, for lepers, so that altogether in the year 1856 there were about 235 lepers in hospital. In 1861 were opened two new asylums, one in Molde, the other in Trondhjem (Drontheim), and as is seen inTable IV(p. 145), since that time a large number of lepers have been admitted to these institutions.
We may regard the numbers in thisTableup to 1885 as accurate; for the later years corrections will have to be made from the later enumerations, which may detect older, concealed cases. But these can only affect the figures to a limited degree.
If we consider theTableclosely, we see that in the first quinquennium (1856-60) the total number of lepers is 76 less, while those in their own homes are 380 less; during this period 585 lepers were admitted to the asylums. The number of lepers as a whole, then, was not much reduced, but atthe end of the period there were 380 lepers fewer at home, or, in other words, there were among the people 380 fewer sources of infection, and to this we ascribe it that while the number of new cases was 1,148 in the years 1856-60, it fell in the years 1861-65 to 1,028. The mortality of the year 1856 we do not know; in the four following years 981 died—668 at home, in the asylums 313. If we assume that there died at home as many in 1856 as in 1857, viz., 230, then the number of deaths at home during the quinquennium would have amounted to 898, and the whole mortality, adding the 313 who died in the asylums, would have been 1,211—only 109 more than the new cases. But one must not so reckon. There died, especially in the early days, a much larger proportion in the asylums than outside; and it is evident, secondly, when one observes the figures in a district from which at the commencement only very few cases were sent to the asylum, that the new cases are much more numerous than the deaths. In Nordmoere, for example, the number of new cases from 1856-60, was 81; that of deaths, 46; only 14 were sent to the asylums, and the disease increased during the quinquennium, the cases rising from 105 to 119. One finds the same thing in Soendmoere—new cases 104, deaths 42, sent to asylums 28; number of cases in 1856, 178; in 1860, 195. In these two districts, then, the disease was evidentlyon the increase, and this would probably have been the case throughout the country, had many cases not been removed from their homes to the asylums; as, for example, in Soendfjord. Here there were, in 1856-60, 214 new cases, 116 deaths, 211 sent to the asylums; number of cases 1856, 431; 1860, 306. If we examine in this way the numbers in the different districts, we find everywhere that decrease of the disease depends on the numbers isolated in the asylums. Where isolation was insufficient or absent, there was no decrease, but either the numbers increased or remained stationary; where, on the contrary, isolation was thorough, the decrease was invariable. This can only be explained in one way, viz., that isolation is the cause of the decrease, and isolation can only have effected improvement by removing from the homes of the people the sources of infection. Further, during the next five years, the number of new cases in those districts where isolation was good continued to sink; where there was none, or it was insufficient, the numbers either rose or remained almost stationary. We will once more compare Nordmoere with Soendfjord. In Nordmoere, in 1856-60, 81 new cases, 14 sent to the asylum; 1861-65, 88 new cases. In Soendfjord, 1856-60, 214 new cases, 211 sent into asylums; 1861-65, 146 new cases.
We consider it superfluous to point out furtherhow the isolation of the patients has caused the decrease of Leprosy in Norway. It is not possible to explain the action of isolation by the elimination of heredity; the time is too short for that. The only one possible solution is that which we have given, and therefore we regard this decrease of Leprosy in Norway following on isolation as the best proof of the contagiousness of Leprosy. Leprosy is, then, according to our view, a contagious disease, and only contagious, not hereditary.
How Leprosy is “caught,” we do not know, but we think it is probably by inoculation; and the nodular form must be more dangerous than the maculo-anæsthetic. This last statement seems to be confirmed by the fact, that in Sogn, where 56.6 per cent. of the cases are nodular and 43.4 per cent. maculo-anæsthetic, the increase varies between 8. and 10.8 per cent., while in Soendfjord, with 72.6 per cent. nodular, and 27.4 per cent. maculo-anæsthetic, it is between 14.4 per cent. and 19.5 per cent. In the nodular form there are incomparably more bacilli than in the maculo-anæsthetic, and in the latter there is no discharge containing bacilli, which in the former is almost always present. It is not improbable that Leprosy may be conveyed by the clothes. We know of one case in which a young man became affected one year after he had worn a pair of old drawersgiven him by a leper. The same thing happened to another young man who wore several pairs of his leprous father’s stockings.
Although we are not acquainted with the spores of the Lepra bacillus, it is quite conceivable that the bacilli are spore bearing. Unfortunately, we know of no method of determining whether the bacilli are alive or dead, and therefore Arning’s observation of the bacilli in the fæces does not decide the question as to whether the bacilli can live for any time outside the body, even admitting that the bacilli which Arning found were actually Lepra bacilli.
After completing this work I received “The Recrudescence of Leprosy and its Causation,” by William Tebb. The author seeks to prove that leprosy is everywhere on the increase as the result of the introduction of vaccination. The book as a whole is directed against vaccination as dangerous. Distinct proofs for his contention that leprosy may be conveyed by vaccination from arm to arm, the author, to our thinking, does not supply. Since Dr. Arning found lepra-bacilli in the contents of vaccine vesicles in lepers, the possibility of the communication in this way can scarcely be denied. But that it can be frequent, I cannot possibly believe. In Norway, vaccination has been compulsory during all those years in which leprosy has steadily diminished. In 1891 Iput the question to all those doctors in Norway who had anything to do with leprosy, whether they had ever met in their practice with a case which could be ascribed to vaccination. Not a single one had observed such a case. And yet, here in Norway, lymph must often be taken from the children of leprous families. But since leprosy is very rare in children, it is evident that leprosy cannot be conveyed in this way. That vaccine vesicles in the non-leprous members of leprous families contain lepra-bacilli is incredible.