492 PROTOZOOLOGY 



mature gametocyte is estimated to be about four days; smoothly 

 rounded body, occupying almost whole of the enlarged erythrocytes; 

 brown haemozoin granules numerous. Macrogametocytes are about 

 9-lOju in diameter, stain more deeply and contain a small compact 

 nucleus; microgametocytes are a little smaller (7-8jU in diameter), 

 stain less deeply and contain a less deeply staining large nucleus. 



The benign malaria fever is the commonest and the most widel}" 

 distributed species in the tropical and subtropical regions as well as 

 in the temperate zone. It has been reported as far north as the Great 



a 





^, 



I ) k I 



Fig. 228. Plasmodium vivax, X1535 (Original), a, young ring-form 

 b, c, growing schizonts; d, two schizonts in an erythrocyte; e, f, large 

 schizonts; g-i, schizogonic stages; j, fully developed nierozoites; k, macro- 

 gametocyte; 1. microgametocyte. 



Lakes region in North America; England, southern Sweden and 

 northern Russia in Europe; and as far south as Argentina, Australia, 

 and Natal in the southern hemisphere. Generally speaking this spe- 

 cies predominates in the spring and early summer over the other 

 species. 



P. falciparum (Welch) {Laverania malariae Grassi and Feletti; P. 

 icnue Stepens) (Fig. 229). The subtertian, malignant tertian or aesti- 

 vo-autumnal fever parasite; schizogonic cycle is somewhat irregular, 

 though generally 36-48 hours. Ring forms: Much smaller than those 

 of P. vivax; about 1m in diameter; marginal forms and multiple 

 (2-6) infection common; nucleus often rod-form or divided into two 

 granules; in about 12 hours after paroxj^sm, all schizonts disappear 

 from the pei-ipheral blood. Growth and schizogonic stages: These are 



