PLASMODIUM 



507 



more or less rounded nucleus excentrically placed and poor in 

 chromatin, and a cytoplasm full of granules and pigment. 



The microgametocyte is characterized by having a large nucleus 

 extending like a band across the cytoplasm, and much chromatin, 

 a clear protoplasm, and less pigment. 



The macrogametocyte and microgametocyte are the means of 

 propagating the parasite in the mosquito, and if they fail to reach 

 the gut of this insect the microgametocytes die off. 



The macrogametocytes, on the other hand, are extremely per- 

 sistent, and can wait in the body for a long time until some chill 

 or accident lowers its resistance, when they become active and 

 develop merozoites by parthenogenesis, thus accounting for the 

 relapses and the recurrences of malaria, even months and years 



' - ^^^^^^^ 



Fig. 166. — ScHizoGoisiY m Plasmodium Fig. 167.— Oocyst in Stomach of 

 vivax (Grassi and Feletti, 1890). Anopheline Mosquito. (X 1,000 

 (X 1,000 Diameters.) Diameters.) 



(By Norman; given us by J.J. Bell.) (By Norman, from a preparation 



by James.) 



after having left a tropical country. Hence in malaria there is a 

 latent phase which is capable of lasting an unknown time — ^at least 

 one to three years, perhaps longer; but upon this subject more 

 will hi) said later, and, indeed, more information is urgently needed. 



In developing parthenogenetically, the nucleus of the macro- 

 gametocyte divides into two portions, one rich and the other poor 

 in chromatin. The pigment granules gather round the pale nucleus, 

 and with it the surrounding cytoplasm and haemozoin form a sort 

 of nucleus de reliquat. The rest of the protoplasm, rendered clearer 

 by loss of its haemozoin, contains the nucleus rich in chromatin, 

 which now divides like the nucleus of a schizont, and forms mero- 

 zoites, which, escaping from the red cell, infect red corpuscles, and 

 start the cycle of schizogony anew. 



Etheogenesis is unknown in the malarial parasite. 



If a female mosquito (the male does not suck blood) belonging to 



