RESEARCHES
ON MALARIA
83
18. Darjeeling district (August—September, 1898). Kala-dukh. It was mentioned
at the end of section 14 that I myself had proposed to Government that kala-
azar should be included in the programme of my year's special duty; because
I then hoped that this disease might shed light upon the mosquito theory; but
now when the theory was established and it was necessary to press on with the
study of the human malaria, I wished to escape this additional duty, as I dread
-
ed lest it should involve me in much pathological work which would interfere
with the principal line of research. I hinted as much to the Director General,
but was told that he expected me to adhere to the programme. The disease
was exciting much comment because it was new and was taking some thou
-
sand lives annually in Assam; but it was forgotten that malaria, though it is
not new, takes some millions of lives annually in India alone!
Harold Brown had recently studied a disease which existed at the foot of the
Darjeeling mountains, and which was called kala-dukh (black sickness) and
was evidently closely allied to kala-azar (black fever). Consequently I obtained
permission to investigate this disorder first, partly because an opportunity
might be afforded me of making further studies at the same time on malaria
in my old haunts at Punkabari. Fixing my head quarters at Kurseong in the
hills on the road to Darjeeling, I made numerous visits to this locality, but was
dogged by ill-luck. The plague-scare, though waning, was still present; and
difficulties of transport impeded the work. On the 25th August I arrived at
Naxalbari, an intensely malarious plantation and village on the plain beyond
the foot of the hills, and found swarms of small and large dappled-winged
mosquitoes (probably Anopheles listoni and A. rossi). There was no time to
make formal experiments, and the people would not have allowed them; but
I examined some dozens of these mosquitoes caught in the houses of infected
persons, both for the pigmented cells and the thread-like bodies; but without
success.* Nearly all my time was however taken up in pathological enquiries
on kala-dukh - as I feared would be the case. But now it was no longer possible
to postpone the evil hour without dereliction of duty, and I was obliged to set
out on the long journey to Assam.
19. Assam (September—November, 1898). Kala-azar. I arrived at Nowgong,
the centre of the epidemic of kala-azar, on the 13th September. It was at once
obvious that my worst fears were well-founded, and that I would be plunged
* How unfortunate I was in this respect may be gathered from the papers of Stephens and
Christophers
71
who later found many of these mosquitoes infected in this very district.
84
1 9 0 2 R.R OS S
for months into a difficult pathological problem and a long pathological re-
port. But the work was not without interest, and I may be pardoned for touch-
ing upon it briefly. The disease had been first noticed by McNaught in 1882.
A few years later Government sent Giles to investigate it; and Giles, who
probably did not come much in contact with the real disease, seemed to have
been considerably misled, and in a report (which was nevertheless a very able
one) pronounced the malady to be ankylostomiasis
77
. Many of the practi-
tioners in the
locality were not satisfied, however, and in 1896 Government
sent Rogers to make a further report. Rogers certainly saw the real disease and
concluded that it was a virulent form of malaria
78
. As it was evidently com-
municable, this implied that he held malarial fever to be communicable - a
thing which no one would believe at that time; but he maintained his opinions
with great courage and success. I was now sent in order, if possible, to decide
the question; and as my researches had shown that contrary to accepted views
malaria must be communicable from the sick to the healthy, Rogers’ position
was justified. But the exact nature of kala-azar still required definition; and, as
I
was called upon to judge between opposite opinions, I was forced into a
tedious enquiry - though it was my immediate personal impression that the
disease is malaria.
Mixed with the cases of kala-azar there were numerous cases of ordinary
malaria; and I found that the local practitioners could not distinguish which
was which until the cases became exceedingly severe, when they were declared
to be kala-azar. This generally happened only in the later stages of the cases - so
that in fact kala-azar seemed to be simply another name for a very severe and
frequently fatal form of malarial cachexia. As, moreover, many of the pa-
tients had ankylostomes, those who are familiar with the subject will under-
stand that my task was indeed a complex one. The plague-scare not having
penetrated here, I attacked the problem by examining the blood of all the
cases, both of malaria and of kala-azar. My results showed that while the para-
sites were easily found in the early cases, they became more and more scarce as
the disease advanced; until, in the old typical cases of malarial cachexia and
kala-azar
neither parasites nor pigment were to be found, even in blood taken
from the spleen. I inferred then that kala-azar is probably only malaria, though
it was possible that some secondary infection might account for the gravity of
the cases. I also inferred - what no one would accept before then - that the
spontaneous disappearance of the parasites must be due to the gradual estab-
lishment of immunity; and that the low fever present in these old cases was
due, not to the parasites, but to some secondary intoxication from the greatly