MALARIAL PROPHYLAXIS— SEGREGATION 
later, while still high fever and severe symptoms continued, parasites might be entirely 
absent. Nor was it exclusively in cases where quinine had previously been taken that 
parasites were absent. In certain cases, though we believe these are comparatively 
rare, parasites may be absent, or if present, are so few in number that they bear no 
proportion to the severity of the attack. And, indeed, our experience has been con- 
firmed by others working both in the tropics and in Europe, by Celli, Ziemann, 
Schaudin.* Thus the last named says, in case I, parasites were present during the 
attack and during the intervals of the lever, but in case II they were almost always 
absent on the day after the attack, and during the attack they were very scanty, 
although the fever was extraordinarily severe. 
We were led then, in such cases as these, to seek for other proofs of the 
malarial origin of the fever. Two such methods were adopted by us : the first consisted 
in a thorough search in extensive blood films for pigmented leucocytes, which are 
evidence of a recent attack of malaria. The second was by a determination of the 
relative proportion of the different varieties of leucocytes in the blood. We followed 
out this line of observation at length, and found that in malaria a relative increase of 
the large mononuclear leucocytes took place, and were led to consider a value as high 
as twenty per cent, as evidence of an antecedent malarial attack. Similar observations 
had also led Turk, whose work was then unknown to us, to point out the diagnostic 
value of this increase in the diagnosis of malaria. We have, then, two auxiliary 
methods in the diagnosis of malaria : — 
1 . The detection of pigmented leucocytes. 
2. The increase in the percentage of the large mononuclear leucocytes. 
Applying these subsidiary tests to blackwater fever in which parasites are, as 
a rule, absent, we were able to show that nearly all of these cases, apparently non- 
malarial, are, in fact, malarial, presenting pigmented leucocytes and an increase in the 
large mononuclear leucocytes. In our first series of sixteen cases, although only in 
three were parasites found (about 19 per cent.), yet using these subsidiary tests no 
less than 93-7 per cent, were shown to be malarial. 
We thus, as a result of our work, established, on a microscopical basis, the 
proof of what had been previously mainly conjecture. 
Blackwater fever, then, is malarial in origin. It cannot, however, be considered 
as simply a severe form of malarial fever, for there is yet another side to the question. 
In i860, Tomaselli first published a series of cases in which symptoms of 
blackwater fever followed upon the administration of quinine, not necessarily in large 
doses, but almost invariably in those who had suffered much from malaria. 
A. Plehn and F. Plehn, in the Cameroons, have published most accurate 
histories of very many cases of blackwater, and with very rare exceptions they always 
followed upon the administration of quinine. 
* Arbeiten, a. J, k. Gesundheitsamte, s. 234, Bd. xix. 
