HJEMOGREGA RINIDM 



481 



Infection of the rat takes place by ingestion of the mite, when the sporozoites 

 are liberated by the juices of the duodenum, and become actively motile 

 striated vermicules, which penetrate the intestinal villi, enter the blood stream, 

 and are carried to the liver, into the cells of which they penetrate, and start 

 the cycle of schizogony. 



As the mites leave the rats during the day-time, and only feed on them 

 during the night, it is easy to understand the manner in which the disease 

 spreads from the sick to the healthy. 



Variations in the Life-Cycle. — 

 The life-history of H. muris is 

 peculiarly interesting, because it 

 is fully known, but it is not quite 

 typical for all haemogregarines, 

 for in it the gametocytes alone 

 are found in the peripheral blood, 

 and they are enclosed in leu- 

 cocytes. 



Other species, however, show 

 marked differences from H. muris, 

 for the majority are found in red. 



Fig. 149. — Hcsmogregarina vitiates 

 Robertson, showing Schizo- 

 gony. 



(After Miss Robertson.) 



Fig. 1^0.— Hcsmogregarina rarefaciens 

 Sambon, showing Male and 

 Female Schizonts. 



(After Sambon.) 



not white, corpuscles, while in some the whole process of schizogony is 

 completed in the blood stream; therefore a few more general remarks are 

 necessary to supplement the life-history given above. 



Fig. 151 . — Hesmogregarina rarefaciens Fig. 152. — Hcsmogregarina seligmanni 



Sambon: Young Gametocyte. Sambon, showing Capsule and 



c \ Cleavage Lines. 



(After Sambon.) 



(After Sambon.) 



The peripheral blood of the vertebrate can contain trophozoites, schizonts, 

 and gametocytes lying either in red or white corpuscles, the two latter bemg 

 contained in a double capsule, which is probably formed by the parasite, 

 and which is always in close attachment to the nucleus of the host cell. 



Schizogony begins with the young trophozoite lying free m the enclosmg 



