Our knowledge ol this form ot malarial lever is relatively recent, dating back only to the beginning of the fifties. Among Torti's otherwise complete descriptions there is no suggestion of blackwater fever. This is explained by the fact that it is endemic in tropical and subtropical regions, and only exceptionally occurs in higher latitudes, and only then when it is introduced.

The first reports of this peculiar, and in many ways interesting, affection, the genesis of which is not yet fully understood, came from French naval physicians, who observed it at Mayotte and Nossi Be (Lebeau Daulle, Le Roi de Mericourt). It was likewise physicians of the French marine who showed its occurrence on the west coast of Africa and in America (French Guiana, the Antilles), and gave a complete description of the clinical picture (Dutrouleau, l'Herminier, Barthelemy-Benoit, Berenger-Feraud, Pellarin, Corre, O'Neill, and others).

The chief seat of blackwater fever is the west and east coasts of Africa. [It extends along the west coast of Africa to Nigeria, Kamerun, the Kongo, Portuguese West Africa, but whether further south than Damara Land is uncertain. It is commonly met with in British Central Africa, British East Africa, Uganda, German East Africa, and south as far as Delagoa Bay, if not further. In Madagascar, Mauritius, Bourbon, and the Comoro Islands it is also known. In the Sudan cases are now being reported from the district of Bahr el-Ghazal, and on the western side as far north as Kayes. It occurs also in Algeria, but not commonly.-Ed.] [It occurs also in Java, Sumatra, and New Guinea, and in parts of Cochin China and Tongking. In America it occurs in most of the Southern States, in French, Dutch, and British Guiana, in Central America, Nicaragua, Costa Rica, Venezuela, and in Cuba, and also probably not uncommonly in Brazil. In the European fever countries it is seen in southern Italy and Greece, Sicily, Sardinia, and also in Merv (Russia), and it is quite common in Palestine.-Ed.] According to Pampoukis' statistics, there occurred in Greece, among 34,937 malarial cases, 0.7 per cent, with hemoglobinuria. In Algiers Laveran saw one single case. [In India we know of three foci-(1) The Duars and Terai and Assam; (2) the Jeypore agency in Madras; and (3) the Canara district in Bombay presidency.-Ed.]

The general experience is that blackwater fever occurs almost exclusively in persons who have lived for a long time in severe malarial regions and have suffered several times from malaria . Berenger-Feraud found, among 185 patients with blackwater fever, but one who had dwelt in the region only three months, and but ten less than a year, while 42 cases occurred in the second year of residence, 79 in the third, 37 in the fourth, 9 in the fifth, and the remaining 8 later. We may say, in general, that it is a rarity to see a person attacked within the first half year of his residence in any one of the previously mentioned regions.

This fact, confirmed on all sides, constitutes the basis for the theory, frequently suggested, that repeated infections with malaria create an individual predisposition which acts as a groundwork for the disease.

The concrete factors of this acquired predisposition have not yet been explained. Some authorities attribute it to the anemia, while others consider this of no special moment.

The clinical course, as described by the early French workers in this field, leaves no doubt that blackwater fever is an expression of malarial infection. Moreover, the blood examinations of recent years, confirming the presence of the malarial parasites in these cases, have made it absolutely certain. [We append here the result of a series of microscopic examinations made by competent observers.

It is evident, therefore, that it is of great importance when the blood examination is made. In those cases examined before the onset of the attack, parasites are practically always present. They then rapidly disappear, but even in negative cases we often have evidence of a malarial infection in-(1) The presence of pigmented leukocytes; (2) an increase in the percentage of large mononuclear leukocytes. -Ed.]

Yersin found, in the urine of two cases, small bacilli lying on the renal epithelium. He cultivated them and found them pathogenic for mice and rabbits. He drew from this the conclusion, hasty in our opinion, that blackwater fever has nothing to do with malaria . Further, we miss from Yersin's paper the blood findings. Breaudat found the same coccobacilli in the urine in five cases, and identified them with Bacteria coli, while Berthier, under strict precautions, found the urine sterile.

Having thus fully determined that blackwater fever is, at least in certain cases, a malarial infection, due in most cases, but not always, to the malignant tertian parasite, it is necessary to assume that the individual predisposition has other causes than repeated malarial infection. One of these is generally considered to be the tropical climate.

In addition to these two principal factors in the creation of the individual predisposition there are probably other auxiliary ones.

As such an auxiliary factor, alcoholism has been frequently suggested, and not only chronic alcoholism, by diminishing the resisting power of the organism, but also acute alcoholic intoxication, which is not rarely immediately followed by an attack of blackwater fever.

Corre, Karamitsas, and Berthier attribute a causal role to cold, though the general facts do not bear them out. Their theory was probably based on the ground of Lichtheim's paroxysmal hemoglobinuria ex frigore.

Berenger-Feraud noticed that, among the affected, there was a comparatively large number who had just taken the mercury cure, and he attributed to the mercury an injurious effect on the resisting power of the red blood corpuscle. Again, syphilis has been suggested as the more important factor, and this conclusion becomes more probable when we recall the analogy of the paroxysmal hemoglobinuria with similar symptoms in syphilis (destruction of the red blood corpuscles).