OF THE ALIAIENTARY TRACT 227 



reported instance of the occurrence of this species. 

 This conclusion is based upon the preciseness of Vir- 

 chow's record which would necessitate the organism 

 being much smaller than that seen since 1915 and 

 named by Wenyon Isospora belli. 



Wenyon is inclined to think that Isospora hoiniins 

 will be rediscovered upon careful examination of the 

 mucosa of the small intestine. 



It seems that Isospora hominis is like the small 

 form of Isospora bigemina of cats and dogs and that 

 it probably spends its life in the subepithelial tissues, 

 where the oocysts reach maturity. 



The oocyst, in that event, should be about one-half, 

 or less, the size of Isospora belli. It should produce 

 two sporoblasts and sporocysts, each with four sporo- 

 zoites and residual body, in the matured stage. If 

 otherwise comparable to the small form of Isospora 

 bigemina in cats and dogs, its immature oocysts are 

 not released into the lumen of the intestine ordinarily, 

 and so examination of feces would usually fail to re- 

 veal the presence of the infection. Since it should 

 mature in the interstitial tissue of the villi, the oocyst 

 would be liberated only on disintegration of a diseased 

 villus, and in mature form with two sporocysts con- 

 taining four sporozoites and residual body each. 



This is virtually a challenge to pathologists doing 

 postmortem examinations to discover this infection 

 by more careful microscopic section of the small in- 

 testine 'or by scrapings. That is, unless Virchow saw 

 an accidental infection of man by /. bigemina from 



rAat>>/CV? 



