Page:Tropical Diseases.djvu/29



Definition.—Morbid conditions produced by certain protozoal parasites belonging to the class Sporozoa, whose definitive host is the mosquito, and whose intermediate host is man and, possibly, other vertebrates. In man these parasites inhabit the red blood-corpuscles, giving rise to fever usually of a periodic character, anaemia, enlargement of the. spleen, and the deposit of a black pigment in the viscera and elsewhere. Some of their phases are amenable to quinine.

The history of malaria goes back to times of remotest antiquity. Already in the fifth century B.C. Hippocrates recognized the existence of periodic fevers, and divided them into quotidian, tertian, subtertian, and quartan. Galen, Celsus, and other Roman writers also gave accurate descriptions of these fevers.

From the classic period until about the middle of the seventeenth century there was no material advance in knowledge regarding malaria, but the introduction of cinchona in 1640 enabled Morton and Tort to separate the malarial fevers from other febrile diseases, and to show that some continued and remitting fevers belong to the same group as the intermittents.

The next important step was the discovery of the characteristic pigmentation of the viscera in malaria.