22 



Fig. 180. Developmental cycle of plasmodium vivax, the tertian malarial 

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

 diameters: i, Sporozoit; 2, penetration of a sporozoit into a red UoocUcorpuscle; 

 3 and 4, schizont developing in the red blood-corpuscles; 5 <lnd 6, nuclear 

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

 3), merozoits entering red blood-corpuscles, and multiplying by schizOgony 3 

 to 7; after longer continuance of the disease the sexual forms arise; ga to i2a, 

 macrogametocytes; gbto i2b,microgametocytes still in the circulatory blood of 

 man. If the macrogametocytes (i2a) are not taken into the alimentary canal of 

 the mosquito, they multiply parthenogenetically (i2a, I3C to i7c) and the 

 resulting merozoits (i7c) become schizonts (3 to 7). The figures below the 

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

 (13 to 17); i3b and i4b the formation of microgametocytes; i3a and i3b, matura- 

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



