69
Paras. 39 & 40
enlargement of the organs accompanied by a low fever. If so, the
disappearance of the parasites and melanin occurs also in British
Guiana, and possibly in other localities, and must be explained.
The theories attempt this explanation. They endeavour to show :—
1. That a malarial infection consists of a continued pervasion of the
blood by the parasites, which, however, in normal untreated cases increase and
diminish in numbers in alternating periods, corresponding with the alternating
periods of fever and apyrexia (paragraph 29).
2. That this continued parasitic pervasion tends toward extinction, either
by spontaneous exhaustion or by the gradual establishment of immunity in
the host (paragraph 29).
3. That special conditions, especially those in which kala-azar occurs, are
likely to accelerate this process of extinction of the parasites (paragraph 30).
4. That the species of parasite concerned is likely to influence the amount
of melanin deposited in the organs and, therefore, the period in which it is got
rid of (paragraph 31).
Reviewing the subject, we see that :—
1. The alternative (a) given above is exceedingly inacceptable. No
observations of a disease exactly like malarial fever but in which either the
parasites or melanin have not been found in the early stages on exhaustive
examination are on record. It is highly improbable that two diseases should
present such close pathological similarities, and that one should exist only within
the boundaries of the other and yet be essentially different (paragraph 33).
2. The alternative (b) can be inacceptable only on one ground, namely,
that melanin once deposited can never be eliminated under at least a year
or so. In the absence of precise knowledge as to how long the elimination
of melanin requires, we are not justified in admitting this (paragraph 33).
To come to a conclusion then :—
The probabilities against alternative (a) are very great ; but the only final
objection against alternative (b) is one based upon a postulate which is not
proved, and which is scarcely even probable.
Unfortunately, in the science of medicine we can seldom attain to the
absolute proofs of the exact sciences, and when we say that a given issue is
proved or disproved we must imply as a rule only that the probabilities for or
against it are very large.
Speaking entirely in this sense, I am willing to say that I think alternative
(a) must be abandoned.
I am, therefore, of opinion, after a very careful survey of the question—
and, I may add, an entirely impartial one, so far as I am concerned—that
though the objections to the malarial theory of kala-azar are serious enough to
require minute scrutiny, they are not strong enough to withstand the nume-
rous facts in favour of the theory. I think, then, with Rogers, that kala-azar
is malarial fever.
40. The Pathology and Epidemiology of Kala-Azar.—Conclusions
regarding details of the disease may be briefly added here.
I have already expressed my views of the symptomatology in paragraph 6.
The course of the malady is divided into three stages, the characteristics of
which are : —
Recurrent conflagrations of high fever with rapid enlargement of the
spleen, and generally also of the liver in the first stage.
Great tumefaction of the organs with low fever in the second stage.
Cachexia, with gradual decrease of the organs, disappearance of the low
fever, and, frequently, intercurrent attacks of pneumonia or dysentery in the
third stage.
I think that the first stage is chiefly that of the parasitic invasion ; the
second stage that of the secondary effects of the invasion ; the third stage
that of the tertiary effects, namely, the result of the secondary effects.
Thus, the beginning and the end of the second stage should be marked by
the beginning and the end of the low fever. At first we have only the manifes-
tations of the parasitic invasion, consisting of repeated attacks of typical
malarial fever ; gradually, as the system begins to feel the effect of the invasion
on the organs, the low fever sets in ; finally, unless death has occurred, recupera-
tion is attempted in the face of the conditions left by the previous stages.