594 MALARIAL FEVER 



mented quotidian ; and (3) a malignant tertian parasite, though 

 the morphological differences described were slight. Further 

 observations have, however, thrown doubt on this distinction, 

 and the evidence rather goes to show that there is a single 

 species. Opinion also varies as to the cycle of this parasite ; 

 according to some observers it is twenty-four hours, according to 

 others forty-eight hours, though there is more evidence in 

 support of the latter view ; and the term " malignant tertian " 

 is frequently used. The fever is often of an irregular type and 

 multiple infection is probably common. Although the question 

 cannot be considered as finally settled, we shall speak of three 

 species of human parasites. The zoological position may be 

 shown by the following scheme, generally followed by English 

 writers, the terminology being chiefly that of Grass! and 

 Feletti : 



Family : H.EMAJVKEBID^ (Wasielewski). 



Genus I. Hsemamceba. The mature gametes resemble in form the 

 schizonts before segmentation has occurred. 



Species 1. ffcemamceba Danileicski or halter idiuin. 

 Parasite of pigeons, crows, etc. 



Species 2. ffccmamceba rclieta or proteosoma. 

 Parasite of sparrows, larks, etc. 



Species 3. Hccmamccba malaria;. 



Parasite of quartan fever of man. 



Species 4. Hcemamceba vivax. 



Parasite of tertian fever of man. 



Genus II. Hsemomenas. The gametocytes have a special crescentic 

 form. 



Species : Hccmomenas prcccox. 



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 



