It is quite true that blackwater fever generally occurs in persons who have previously suffered or are suffering from malaria; but this does not prove that it is a special manifestation of malaria. It may be concurrence merely. We do not believe tuberculosis to be a peculiar manifestation of enteric fever because it often follows in the wake of that disease. Mpreover, as already pointed out, blackwater fever frequently attacks people who previously had never had a single paroxysm of intermittent fever. The fact that malaria parasites are often found in the early stages of blackwater fever is not surprising when we consider that in many places malaria is exceedingly common and is co-endemic with blackwater fever. Although the tertian and quartan parasites have been found in the blood of blackwater-fever cases, the parasite which most frequently occurs is the subtertian, because it is that species of malaria parasite which is most common in the endemic regions of black- water fever. Yet of all the intermittent fevers, subtertian is the one that differs most, clinically, from blackwater fever. It is true that subtertian varies considerably in different cases; but the type of the disease does not alter, and the number and distribution of the parasites in the organs are always in perfect accordance with the intensity and nature of the various symptoms. In no case of subtertian, not even in the most pernicious, do we ever find the symptoms peculiar to blackwater fever. On the other hand, all cases of blackwater fever, however grave, however mild, always exhibit the same characteristic symptoms, with no difference other than as regards intensity and duration. Admitting the malaria theory of blackwater fever, we should have to consider a mild relapse of blackwater fever to be an unusually severe attack of subtertian an untenable paradox. When malaria parasites are found in cases of blackwater fever they may be very scanty and in no way proportional to the symptoms of the disease. But in many cases no parasites are found; or, what is still more striking, if there were a few parasites before the attack, they invariably completely disappear with the onset of
