608 PROTOZOOLOGY 



children. History of malaria (Ross, 1928; Boyd, 1941; Russell, 

 1943); general reference (Boyd, 1949; Russell, West and Manwell, 

 1946); antimalarial drugs (Russell, 1952a). 



It must be added here that human ingenuity has been for nearly 

 30 years utilizing the malarial organisms in combating another dis- 

 ease; namely, naturally induced malaria therapy has been success- 

 fully used in the treatment of patients suffering from general paresis 



C 



* V 



c 



f Q h 



r t+f t 



i i k I 



Fig. 259. 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 merozoites; k, macro- 

 gametocyte; 1, microgametocyte. 



and other forms of neuro-syphilis. Technique (Boyd and Stratman- 

 Thomas, 1933; Boyd, St.-Thomas and Kitchen, 1936a; Boyd, St.- 

 Thomas, Kitchen and Kupper, 1938; Mayne and Young, 1941). 



P. vivax (Grassi and Feletti) (Fig. 259). The benign tertian malaria 

 parasite; schizogony completed in 48 hours and paroxysm every 

 third day. Ring forms: About 1/4-1/3 the diameter of erythrocytes; 

 unevenly narrow cytoplasmic ring is stained light blue (in Giemsa) 

 and encloses a vacuole; nucleus stained dark-red, conspicuous. 

 Growth period: Irregular amoeboid forms; host cell slightly enlarged; 

 Schuffner's dots begin to appear. Grown schizonts: In about 26 hours 

 after paroxysm; occupy about 2/3 of the enlarged erythrocytes, up 

 to 12^ in diameter, which are distinctly paler than uninfected ones; 

 Schuffner's dots more numerous; brownish haemozoin granules; a 

 large nucleus. Schizogonic stages: Repeated nuclear division produces 



