762 



THE COCCIDIA 



represents the oocyst stage the last stage in the life history of the parasite 

 in the animal tissues (fig. 361). 



The oocysts then pass into the intestine and are eventually excreted : 

 outside the body of the host they undergo a metamorphosis which renders 

 them capable of setting up fresh infections in other animals (the disease is 

 not directly contagious, or miasmatic as older writers would have termed it). 



FIG. 361. Coccidium cuniculi. Encysted 

 adult forms. (After Blanchard.) 



FIG. 362. Coccidium cuniculi. Extra-cellu- 

 lar life history. C, formation of sporoblasts ; 

 D, transformation of sporoblasts into sporo- 

 cysts. (After Blanchard.) 



Life history. 

 I. Outside the animal body. 



If a number of oocysts be placed in a drop of sterile water x in a Koch's cell 

 and kept at a temperature of 15-18 C. their contents will be seen in the course of 

 2 or 3 days to divide into two, and later, into four small spheres or sporoblasts 

 (fig. 362). Each sporoblast then elongates and forms a sporocyst or cytospore, each 

 of which in turn divides into two nucleated falciform corpuscles, crescent bodies or 

 sporozo'ites, and a granular residuum which is not utilized (fig. 363). 



FIG. 363. Coccidium cuniculi. E, an 

 isolated sporocyst ; s, s, sporozo'ites ; r, resi- 

 duum ; F, an isolated sporozo'ite. (After 

 Balbiani.) 



FIG. 364. Coccidium cuniculi. A, sporpzoiite 

 penetrating an epithelial cell ; B, formation of 

 the schizont. 



II. Infection of the host. 



The cyst containing the sporocysts is highly resistant to external influences and 

 retains its vitality for a long time. When a rabbit swallows such a cyst the capsule 

 is digested and the sporocysts are set free, and these in turn open and discharge the 

 sporozoi'tes. The sporozoites are actively motile and so are able to pass into the 



1 The following method is recommended by Leger and by Laveran for studying the 

 extra-corporeal development of coccidia : Lay the material containing the coccidia on 

 small pieces of charcoal and place the charcoal in watch-glasses containing a few drops of 

 carbolized water (to prevent the growth of moulds and bacteria) and keep the preparation 

 in a moist chamber. 



