Reprint from Courier of Medicine, April, 1894.] 
THE INOCULABILITY OF LEPROSY. 
Tlie question of the manner in which leprosy is transmitted 
and acquired has always been replete with interest. The discus- 
sion on this subject has been an animated one, and many inter- 
esting facts have been brought forward in support of the various 
views advanced. The most ingenious theories have been formu- 
lated and altogether a mass of literature produced which seems 
to have brought us no nearer to the final solution of this com- 
plicated question. It is for this reason that I have felt some 
hesitation in approaching it, yet there is so much that is alluring 
in connection with the subject that one is unconsciously attract- 
ed to it and tempted to give views upon it, albeit they may be 
anything bnt convincing in their nature. In fact, all that I have 
to offer is merely a hint on the subject, with a possible explana- 
tion of the view I have taken that leprosy is a true infectious 
disease and not contagious as that word is known in its ordinary 
acceptation. In other words, an inoculation of a specific char- 
acter must take place in order that the disease may be trans- 
mitted. 
Before doing this, however, I desire to make a general review 
of the prominent theories which have been advanced, in order 
that a clearer view may be arrived at in reference to the partic- 
ular point I desire to lay stress upon. To begin with, we have 
the two great opposing schools respectively contending for con- 
tagion and infection. Among the former are those who bring 
as their mqst convincing proof the spread of leprosy in the Sand- 
wich Islands, where it was an unknown malady before the advent 
of a Chinese leper, who is looked upon as the fons et origo of the 
terrible scourge which has affected the unfortunate inhabitants 
of these isles. We are also given the history of the spread of 
leprosy in ancient times among the Hebrews, and later among 
the Crusaders, which was so great that lazarettos existed 
throughout Europe and the strictest isolation which was en- 
forced served to stamp out the dread malady. We are also 
shown the modern spread of the disease from various foci, the 
whole mass of evidence being certainly very plausible in support 
BY A. H. OHMANN-DUMESNIL. of the theory of transmission by contagion. The claim that 
children born of lepers will become leprous if they remain with 
their parents, but will not suffer from the disease if removed 
early from their progenitors has been apparently demonstrated 
in numerous instances and still further lends an air of proba- 
bility to the contagion theory. In fact, the points brought for- 
ward in support of this view are certainly strong and would 
almost prove convincing were they not opposed by others of an 
equally conclusive character, in favor of infection. 
The upholders of the view that leprosy is acquired by infection 
bring arguments in support of their theory which are chiefly 
based upon modern bacteriological researches. First of all, how- 
ever, the contagiousness seems to be refuted by the fact that the 
superintendents of leper asylums, who have officiated in that 
capacity for y ears and who have operated time and again upon 
lepers have not presented any symptoms of the disease. We 
also know from the travels of Zambaco Pasha that in the Orient 
the lepers have free intercourse with the non-lepers, and yet the 
disease does not seem to spread with any degree of rapidity 
among the latter. In fact, the cases observed seem to be very 
small in number. In Brittany, France, a number of lepers have 
been found and no one suspected that such a colony existed. 
Yet no evidence exists that it ever spread from this focus, a cir- 
cumstance which should certainly have occurred were the dis- 
ease contagions, as the affected individuals had free intercourse 
with those in no wise affected with the disease. We also have 
the well-observed cases on record wherein the children of lepers 
have remained with their parents and reached adult life, betray- 
ing at no time any of the symptoms of the trouble. They were 
exposed to all the conditions demanded by contagion and yet the 
results were negative. We have also a matter of observation 
at this present day of the free intercourse of lepers with non- 
lepers in certain hospitals in Europe, as well as in this country, 
. and there is not yet recorded a case wherein the affected indi- 
vidual transmitted his disease to any one of those with whom 
he came in contact. Finally, there are numerous instances in 
which a leper and a healthy indMdual have married and the 
disease was not acquired by the latter. Were the disease con- 
tagious it certainly stands to reason that the latter would 
acquire it and show some symptoms indicative of its existence. 
As Buret very pertinently points out, in his forthcoming work on “Syphilis in the Middle Ages,” all the published accounts of 
the great epidemic of leprosy which reigned at that time go to 
show that the majority of the afflicted were really suffering 
from syphilis. 
In my opinion, the theory of infection is that which is the 
more reasonable. Mere contact will not reproduce the disease 
in an unaffected individual. It requires something more. There 
must be the introduction of something specific which will lead 
to the development of the disease. So far as modern research 
enables us to determine, this something is the lepra bacillus. 
It is a micro-organism which is sui generis and always found 
in leprous tissues. It is cultivated with difficulty, it is true, 
and not being followed by any positive results when inoculated 
in animals—they being probably immune—we cannot do any- 
thing more than speculate upon what the results might be in 
human beings. For, so far, the very few experimental inocula- 
tions made on man have not been sufficiently crucial to permit 
us to draw any legitimate conclusions. Reasoning from anal- 
ogy, we would be lead to look upon the inoculation of leprosy as 
similar to that which occurs in tuberculosis, although by no 
means as easy a matter. It is this very difficulty of acquiring 
the trouble by accidental inoculation and the apparently facile 
manner in which leprosy has spread in some localities which 
has tended to somewhat confuse the ideas held and has led to 
the diversity of opinion which has resulted therefrom. I do 
not presume to say that I am capable of solving this intricate 
problem, but some of the ideas advanced have led me to the 
formulation of a few possibilities which might, hypothetically, 
account for some of the observed facts. Thus, Mr. Jonathan 
Hutchinson contends that it is in fish-eaters that we find leprosy 
most prevalent, and he concludes that an exclusive diet of fish 
is probably the cause. On the other hand, an intermediary host 
function has been invoked to explain the inoculation by means 
of the lepra bacillus. That is, the organism must first pass into 
a host before it can become an active propagator in man. By 
combining the two it will be seen that a better theory can be 
formulated. The bacillus first obtains a host, be this a fish, a 
vegetable, the soil or what not, and then suffers certain morpho- 
logical changes which render it capable of entering the tissues 
of man and of multiplying there. After having attained full 
maturity, the question again suggests itself as to whether it must not again suiter certain changes before it once more be- 
comes infective. 
There is one point upon which we can reasonably bo certain, 
viz., that inoculation will not take place unless the soil be recep- 
tive. In other words, there must exist that intangible condition 
which is known as susceptibility. The best scientific modern 
accounts will show this in a manner so clear and convincing as 
to leave no room for reasonable doubt. Some races are pecu- 
liarly prone and others seem to be immune. Moreover, certain 
communities which are practically isolated and living under the 
same conditions, moral as well as physical and social, seem to 
retain a susceptibility which dates back as far as the memory of 
man runneth. But that the inoculation is by any means an easy 
matter, or that contagion spreads leprosy, I much doubt. I 
have had occasion to see spontaneous cases in St. Louis and the 
number has not increased. The cases in France reported by 
Zambaco do not seem to have created epidemics. 
In view of all these circumstances, which I have but hastily 
sketched, I would conclude as follows: 
1. Leprosy is not contagious. 
2. It is inoeulable in the same manner that tuberculosis is. 
3. To effect inoculation an intermediary host function is requi- 
site. 
4. In addition, the threatened individual must possess a sus- 
ceptibility to the disease. 
5. There exists no reason for fearing epidemics or pandemics 
of the disease among the Caucasians outside of the few sporadic 
cases which will occur now and then, frequently without any 
adequate cause being apparent.