634 MALARIAL FEVER 



Species 4. ff&mamceba vivax (Plasmodium vivax). 

 Parasite of tertian fever of man. 



Germs II. Hsemomenas. The gametocytes have a special crescentic 

 form. 



Species : Hmmomenas prcwox (Plasmodium falciparum}. 



Parasite of malignant or festive-autumnal fever of man. 



In addition, there are other species belonging to the same 

 family of blood parasites, which infect monkeys, bats, frogs, 

 lizards, etc., especially in malarial regions. 



We shall now give the chief distinctive characters of the three 

 human parasites : 



1. Parasite of Quartan Fever. The cycle of development in 

 man is seventy-two hours, and produces pyrexia every third day ; 

 double or triple infection may, however, occur. In fresh speci- 

 mens of blood the outline is more distinct than that of the 

 tertian parasite, and amoeboid movement is less marked. Only 

 the smaller forms show movement, and this is not of active 

 character. The infected red corpuscles do not become altered 

 in size or appearance, and the pigment within the parasite is in 

 the form of coarse granules, of dark brown or almost black 

 colour. The fully developed schizont has a " daisy-head " 

 appearance, dividing by regular radial segmentation into from 

 six to twelve merozoites, which, on becoming free, are rounded 

 in form. 



2. The Parasite of Mild Tertian Fever. The cycle of de- 

 velopment is completed in forty-eight hours, though a quotidian 

 type of fever may be produced by double infection. The 

 amoebulae have a less refractile margin than in the quartan type, 

 and are thus less easily distinguished in the fresh blood ; the 

 amoeboid movements are, however, much more active, while 

 longer and more slender processes are given off. The infected 

 corpuscles become swollen and pale, and may show deeply 

 stained points by the Romano wsky method "Schiiffner's dots." 

 The pigment within the parasite is fine and of yellowish-brown 

 tint. The mature schizont is rather larger than in the 

 quartan, has a rosette appearance, and giyes rise to from fifteen 

 to twenty merozoites, though sometimes even more occur ; these 

 have a somewhat oval shape. 



In both the quartan and tertian fevers all the stages of 

 development can be readily observed in the peripheral blood. 

 The gametocytes have a rounded form as described above. 



3. The Parasite of Malignant or jEstivo-autumnal Fever or 

 Tropical Malaria. The cycle in the human subject probably 



