164 



SPOROZOA. 



contents contracted into a spherical body with highly refractile 

 granules, and a single nucleus seen as a clear pale area. The 

 oocysts complete their development in one to four days, 

 according to the temperature. The cytoplasm divides into 

 two sporoblasts, which become elongated and covered with 

 cyst- walls. In each sporocyst are developed four sporozoites 

 and a large spherical residual body. Sporozoites are elongate 

 structures, rounded at the anterior and tapering at the posterior 

 end, and with a nucleus lying at the junction of the anterior 

 and the middle third. 



The organism is probably a parasite of the epithehal cells 

 of the small intestine, where schizogony and the development 

 of the gametocytes will be found to occur. 



Fig. 74. — Isospora belli Wenyon. 



A, immature oocyst ; B, mature oocyst. 

 (From Reichenow, after Dobell.) 



Dimensions. — Oocysts 25-33 ju. in length by 12-5-16 /x in 

 width ; sporocysts 12-14 ju, by 7-9^. 



Pathogenicity.— Wenjon (1926) reports an observation by 

 Conrad (1922) on a laboratory worker who accidentally in- 

 gested material containing developed oocysts. Six days later 

 diarrhoea set in and persisted for thirty days. The oocysts 

 were found three weeks after the onset, and persisted in the 

 patient's stools for 12 days, after which they disappeared, 

 and recovery was complete. 



Similar symptoms and similar cysts have been found by 

 a number of workers in different countries, but it is not certain 

 if they belong to one or more species. 



