500 



Fig. 179. — Developmental cycle of Plasmodium vivax, the tertian malarial 

 parasite. Figures i to 17 are magnified 1200 diameters; 18 to 27, only 600 

 diameters: i, Sporozoit; 2, penetration of a sporozoit into a red blood-corpuscle; 

 3 and 4, schizont developing in the red blood-corpuscles; s and 6, nuclear divi- 

 sion of the schizont; 7, free merozoits; 8 (following the arrows to the left to 

 3), merozoits entering red blood-corpusdes, and multiplying by schizogony 3 

 to 7; after longer continuance of the disease the sexual forms arise; ga to 12a, 

 macrogametocytes; gb to 12b, microeametocytes still in the circulatory blood of 

 man. If the macrogametocytes (12a) are not taken into the alirnentary canal of 

 the mosquito, they multiply parthenogeneticaUy (12a, 13c to 17c) and the 

 resulting merozoits (17c) become schizonts (3 to 7). The figures below the 

 dotted line represent what takes place in the alimentary canal of anopheles 

 (13 to 17); 13b and 14b the formation of microgametocytes; 13a and 13b, matura- 

 tion of the macrogametes; isb a microgamete; 16, fertilization; 17, ookinete; 



