222 PROTOZOAN PARASITISM 



swallowed by a host-to-be, the Oocyst and Sporocyst 

 dissolved or burst (19) in the intestine, the Sporo- 

 zoite (6), liberated and active, enters an epithelial 

 cell and the process of asexual multiplication is begun 

 in the new host. 



The transmissible form of the organism, the Spore, 

 is thus seen to be doubly protected, by the Oocyst 

 and the Sporocyst, the whole body resisting exposure 

 and remaining viable under conditions more severe 

 than may be borne by the comparatively non-resist- 

 ant cysts of other intestinal protozoa. 



HABITAT AND EFFECTS 



Although it is not definitely known it is presumed 

 that the coccidia of man inhabit the small intestine, 

 although an infection of the liver has been reported. 



The organisms live during their asexual life in 

 the epithelium of the mucosa, consequently they are 

 essentially pathogenic. The cells w^hich are inhab- 

 ited are destroyed as the organisms mature and be- 

 come free. Naturally so long as this is all that occurs 

 and unless there is sufficient denuding to expose the 

 subepithelial tissues to bacterial invasion, it is not 

 anticipated that any considerable reaction, func- 

 tional disturbance, or symptoms, w^ould occur from 

 it. The loss and replacement of individual cells on 

 the surface of the intestine is probably of constant 

 occurrence under natural conditions. As a matter of 

 fact there is no definite clinical state associated with 



