REPORT
ON THE
NATURE OF KALA-AZAR.
I.-PRELIMINARY.
Limits of the Present Enquiry.—My study of kala-azar was made
under the following circumstances :—On the 17th February 1898 I was placed on
special duty for six months under the Director General, Indian Medical Service,
to investigate malaria and kala-azar. In this work I understood that my atten-
tion was to be devoted principally towards discovering the exact mode in which
infection by malaria takes place. As regards kala-azar, I concluded that the
study of that disease was admitted within the scope of my duties, chiefly because
it had just been pronounced by Captain Rogers, I. M. S., to be a malarial disease,
while it had long been accepted as a communicable one—a combination which,
if Roger's conclusion be correct, promised to make the subject a very profitable
one for enquiry in respect to the principal object of my deputation.
Before commencing actual work the question as to the best means of
attacking the research entrusted to me was considered. It had long been
obvious that the precise mode of infection by malaria could be ascertained only
by the discovery of the life history of the parasites of malaria outside the human
body. The subject was one with regard to which we knew nothing for certain
at the time ; but a little previously some indications had been obtained which
went to show that these parasites can undergo development in mosquitoes. I
decided then to begin my labours by following this clue as far as it would
lead.
The difficulty generally felt with regard to Roger's opinion of kala-azar,
that it is malarial fever, appeared to lie in the fact of the disease being commu-
nicable from the sick to the healthy, whereas in general acceptation, malarial
fever is not supposed to be transferable in this manner—in other words the sub-
ject of kala-azar was bound up in the more general problem which it was my
chief duty to examine. Hence, on all grounds, I felt it better to postpone the
consideration of kala-azar to that of the larger subject ; and may add that I
obtained the permission of the Director General to do so.
I proceeded, therefore, to attack this larger subject at once. The result has
already been reported [ 1 and 2 ], but may be touched on here in view of its
possible applicability to the present subject. Confining my attention to the
malaria of birds, I ascertained by means of numerous experiments that proteo-
soma, Labbe, one of the so-called malaria parasites of birds, is capable of living
and growing in a species of mosquito—a fact which established the truth of the
indications just referred to regarding human malaria [ 1 ]. [Further researches
[ 2 ] showed that the mosquito stage of the avian organisms produces certain
delicate thread-like reproductive elements which have the power of entering the
veneno-salivary gland of the insect ; suggesting that these bodies are meant to
be injected, together with the secretion of this gland, into the wound made by
the bite of the mosquito, thus causing infection in the insect's victim. Easy
and complete proof of this theorem was next obtained by the experimental
infection of healthy birds. Mosquitoes fed a week previously on birds containing
the parasites of avian malaria were permitted to bite healthy birds. Nearly
80 per cent. of these contracted the disease in a few days under circumstances
which leave no doubt as to the infection being due to the bites of the infected
mosquitoes.
These researches occupied six months ; during which, although I was able
to examine cases of malarial fever and ankylostomiasis in the Darjeeling terai,
it had been impossible to touch kala-azar. My special duty was now, however,
extended for another six months, and I felt it time to take up my duties in this
B