780 
PROCEEDINGS OE SECTION I. 
disease abroad return to Europe and live there in quite ordinary con- 
tact with others — sometimes at home, sometimes in the general wards 
of an infirmary or an hospital, and yet do not communicate their 
disease. There is, I believe, but the possible exception I have already 
mentioned, and one or perhaps two others which give ground for 
suspicion. We know also, and on the unusually good authority and 
personal observation of Boeck in 1870 and of Dr. Hansen more 
recently, that 160 lepers who emigrated with their families from 
Norway to some of the Northern States of America, and lived there 
under no restrictions at all, were found on being traced to have com- 
municated their illness to no one — Norwegian, American, or other. 
So that, as regards direct communication of this disease, we may well 
admit that it is a possibility, and yet we can point to well-ascertained 
facts which at least forbid us to regard direct communication with 
the sick as the means by which leprosy is maintained , or to regard a 
leper as constituting any important danger to those who come into 
contact with him. 
Now, if yon feel inclined to disagree with that conclusion (not- 
withstanding your own Australian experience), you will have no 
difficulty in finding a hundred accounts which have been tendered to 
prove that leprosy is easily communicated by the sick, and that the 
disease is so maintained. I have hut one woi'd to say in reply. I 
merely ask you for the future to read those contrary accounts 
critically, and to accept those alone which are recorded with sufficient 
fulness as regards the essential details, and, at the same time, are 
entirely free from the post hoc fallacy. You will find that a vast 
majority of such instances are spoilt from the beginning by having 
been observed on areas of recognised endemicity, so that primary and 
secondary cases alike were under the influence of locality. Apart 
from that, you will find very few indeed which answer to the two 
requirements mentioned — one or both of them.* 
After a not inconsiderable course of study, T take it that in any 
mind seized of the facts, and in the habit of weighing evidence, there 
can be no doubt at all about this: That lepra, if at all communicable 
by the sick, must be so only with great difficulty, and under special 
and quite unknown circumstances. Even some of the w T riters to 
whom I have just referred, and wdio have asserted that leprosy was so 
communicable (though without distinguishing between mere occa- 
sional communication, and such a common or frequent communication 
as would account for its maintenance ), seem dimly to have perceived 
this ; and, consequently, they usually postulate long-continued and 
intimate contact between the sick and the healthy as a necessary 
condition of communication. But you must perceive that this postu- 
late is a sacrifice to a speculative opinion, for the records are full of 
cases of leprosy in which the sufferers never had been in long- 
continued, nor in close, nor in any conscious contact at all w ith any 
* Nearly thirty years ago the Committee of the Royal College of Physicians 
remarked, in their Report (1807), that the cases cited to them in support of contagious- 
ness either rested on imperfect observation or were recorded with too little attention 
to the necessary details to be of service. If tho reader doubt whether it be still 
necessary to make a similar criticism, he need only refer to Dr. Billis’ work, 1881, 
pp. 177 ctscq,, and to a work published more recently (“ Leprosy,” by George Thin, 
M.D., London, 1891), and peruse the very long string of “cases” cited therein, in order 
to satisfy himself that it is so. 
