CHAP. I PLASMODIUM 57 



Fic. 23. 



Life-history of Plasmodium. A-E, Stages of growth and division of schizont within red blood- 

 corpuscles ; A, B, young amoebulae ; C, " rin^ " stage ; D, schizont with divided nucleus ; 

 E, group of merozoites formed by subdivision of schizont ; F, group of merozoites set free by rupture 

 of corpuscle — the granules of melanin are left behind in a loose heap : F-A, the dotted line indicates 

 the repetition of the schizogony cycle; G, amoebulae which will become male ((5) oi^ female (9) 

 gametocytes (H) ; I, fully developed gametocytes lying free in the blood ; J, maturation of the gametes 

 in stomach of mosquito — the upper (9) is extruding its polar body, the lower (cJ) is giving off six 

 slender microgametes • K, syngamy ; L, actively moving zygote (ookinete) ; M, zygote has burrowed 

 into one of the cells of the stomach- wall ; N, it has rounded itself into a sphere on the outer sturface 

 of the stomach ; O, it is increasing in size and dividing into sporoblasts ; P, each sporoblast is 

 developing slender sporozoites over its surface ; Q, large round mass of sporozoites with residual 

 protoplasm ; R, sporozoites set free in blood of the mosquito by rupture of the mass ; S, lobe of 

 salivary gland, sporozoites are seen embedded in the cells of the gland while others have penetrated 

 into the central duct ; T, free sporozoites as injected into man. 



[The schizogony part of the life-cycle (A-F) takes 48 houi-^ in P. vivax, 72 hours in P. malariac. 

 In P. falciparum it is less regular, occupying from 36 to 48 hours. The sporogony part of the life- 

 cycle commonly occupies about ro-12 days.] 



