436 



PROTOZOOLOGY 



infected erythrocytes become enlarged, widely distributed over 

 temperate and tropical countries. 



P. falciparum (Welch) (Fig. 198, h-n). The organism of malig- 

 nant tertian, subtertian, or aestivo-autumnal malaria of man, 

 schizogony completed in 24-48 hours; schizonts adhere to capil- 

 lary wall, to which malignancy of the species is attributed; game- 

 tocytes crescentic (some authors therefore place this species in 

 genus Laverania); of more Hmited distribution in tropical and 

 subtropical regions of the world. 



Fig. 198. a-g, Plasmodium vivax, XlOOO (Kudo); h-n, P. falciparum, 

 XlOOO (Kudo); o-u, P. malariae, XlOOO (Kudo), a-e, h-1, o-s, 

 schizogony; f, m, t, microgametocytes; g, n, u, macrogametocytes. 



P. malariae (Laveran) (Fig. 198, o-u). The organism of quartan 

 malaria of man; schizogony completed in 72 hours; in tropical 

 and subtropical countries. 



Numerous species of female mosquitoes belonging to the genus 

 Anopheles transmit these organisms. In the United States, the 

 chief species concerned is A . quadrimaculatus. 



The malaria parasites are usually studied in (Giemsa, Wright, 

 or Hasting) stained blood films or smears ; the comparison of the 

 three species of human malaria given on the following page is 

 based upon observations of stained specimens. 



A number of species of Plasmodium have been reported from 

 various avian hosts. Manwell (1935) recognizes the following spe- 

 cies as occurring in the United States. Hegner and his colleagues 

 (1938) have called attention to the fact that merozoites enter 

 young red corpuscles or reticulocytes (Fig. 199,/, g). 



