602 Malaria 



the sixth or seventh day with P. falciparum (23, 42). Likewise, P. cathe- 

 merium disappears from the blood of canaries within an hour after 

 inoculation and does not reappear until the end of the third day (118). 

 Coatney, cited by Sapero (90), has found also that large volumes of 

 blood from latent cases of vivax malaria fail to infect the recipients. The 

 latent phase thus resembles the prepatent period in that the blood con- 

 tains no demonstrable parasites. That the parasites are actually present 

 in the host is indicated by the subsequent relapse or primary attack. 



The accumulation of morphological data, culminating in the ob- 

 servations of Shortt and his colleagues on primate malaria, gradually 

 brought to light this previously unknown exo-erythrocytic (E-E) phase 





6 



Fig. 13. 1. Exoerythrocytic schizonts (preerythrocytic phase) of Plas- 

 modium cynomolgi in hepatic cells of Macaca mulatta; schematic (after 

 Shortt). A. Stage recovered on fifth clay after inoculation by mosquitoes; 

 diameter of schizonts, lO-ll^tt. B. Vacuolated schizont recovered on the sev- 

 enth dav of the infection. 



(Fig. 13.1). Non-pigmented E-E stages were perhaps first reported by 

 Raffaele (81), who found them in bone marrow endothelium of birds 

 infected with P. elongatiim and suggested (82) their origin from sporo- 

 zoites. Raffaele (83) later described non-pigmented P. vivax in human 

 bone-marrow five days after inoculation with sporozoites. From other 

 laboratories, E-E stages have been reported in P. gallitiaceum infections 

 (53, 57) and tissue cultures (48, 61), in tissue cultures of P. lophurae 

 (115), in canaries infected with P. cathemerium (121), in P. relictiim (31), 

 in P. mexicaniim of lizards (113), in monkeys infected with P. cynomolgi 

 (95, 97, 100), and from human liver early in a P. vivax infection (95, 99). 

 After inoculation of monkeys (Macaca mulatta) with sporozoites 

 of P. cynomolgi, E-E stages undergo growth and merogony in hepatic 

 parenchyma cells. By the fifth day the schizont approaches \\^ in di- 



