778 
PROCEEDINGS OF SECTION I. 
a factor of more or less importance in determining lepriasis — that is 
to say, whether lepers could transmit a predisposition to their 
offspring — was a question which HirseTi inclined to answer in the 
affirmative. Recent investigations made on a large scale seemed to 
show that at all events heredity exercised no such indirect influence of 
that kind as could be appreciated. The Leprosy Commission in India 
did good work when they pointed out that leprosy in parents was not 
associated with an incidence of leprosy on their children greater than 
the incidence on children horn of healthy parents, and living on the 
same leprosy area, on the one hand; on the other, that the parents of 
lepers were not lepers themselves in any greater proportion than other 
persons living on the same leprosy area whose children were healthy. 
And as to the practical question whether hereditary disposition were 
among the causes of the maintenance of lepra, the Commission showed 
very clearly that it might be excluded from consideration in all 
discussions of that point ; for they showed, first, that lepers produce 
but few offspring at most ; and, secondly, that such as they do 
produce are extremely liable to die at young ages from indifferent 
causes. Probably, then, heredity has no share in determining lepriasis, 
and certainly it has no share in maintaining lepra present among 
mankind.* 
Only one other suggested explanation of the maintenance and 
diffusion of leprosy has received very general attention, and that is 
the contagion hypothesis. In accordance with the opinion I expressed 
at first, I think we cannot do better than follow Hirsch’s account of it. 
Hirsch pointed out, in the first place, that the doctrine of con- 
tagiousness had been in favour from the earliest times ; but, then, 
there is no doubt the diagnosis of leprosy was but ill-established, and 
several other chronic and disfiguring diseases, and especially syphilis, 
were confounded with it. As long as the diagnosis of syphilis con- 
tinued uncertain, so long did the doctrine that leprosy was communi- 
cable by the sick hold its ground. Xo sooner did men begin to learn 
to recognise syphilis with some certainty than the doctrine of the 
communicability of leprosy began to fall into disrepute; and at last it 
came to be almost entirely rejected. But soon after Dr. Hansen’s 
discovery of the B. lepra, in 1871, t opinion began to change again ; and 
when Dr. Xeisser, in 1881, sufficiently established a necessary or 
causative connection between Dr. Hansen’s bacillus and lepriasis, the 
doctrine of communicability began once again to come into favour. 
That doctrine fits in so well with preconceived notions which date 
from antiquity, and is at first sight so natural, so easy, and so complete 
that it is not surprising that many of the profession as well as the 
public in general should have adopted it. But Hirsch pointed out — - 
and his remark has all the force to-day which it had when lie first 
made it — that in reality Dr. Hansen’s discovery did not at all justify 
the inference commonly drawn from it. He said : 46 It is only an 
& priori proof of the conveyance of leprosy by contagion which 
Xeisser adduces, when he states, on the ground of the finding of 
bacteria, and of the hypothesis therefrom deduced, that the malady is 
* On these points compare Report on Leprosy in India, by T. R. Lewis and 
D. D. Cunningham : Appendix to 12th Annual Report of the Sanitary Commissioner 
with the Government of India, 1876. 
f Leprosy : Hansen and Looft, trans. by N. Walker, London, 1895. 
