764 



SARCOSPORIDIA 



and Darling (1910a) showed that guinea-pigs could be infected with the 

 parasite of rats, and Darling points out that the forms in the guinea-pig are 

 morphologically identical with those described by him from man. Erdmann 



Q 





^31 



ch'.spb. 



Fig. 329. — Sarcocystis tenella of Sheep: Diagrammatic Representation of 

 Small Portion of Cyst (x ca. 1,000). (After Alexeieff, 1913.) 



E, Envelope of cyst consisting of three zones — external (Ze.), median {Zm.), and internal (Zi.). 

 The latter is continued as the septa, which divide the cyst into chambers. Outside the 

 envelope of the cyst is a fibrous zone (Zf.), a connective tissue layer (fc). and a muscular layer 

 ()n.). The chambers near the envelope contain the sporoblasts (ch.spb.), which become 

 transformed into spores (ch.sp.). According to Alexeieff, the envelope and the septa arc 

 developed from the tissues of the host, the parasites being the cells which become sporoblasts 

 and spores. 



(1910a) succeeded in infecting mice with the parasite of sheep, while Darling 

 infected guinea-pigs with the form found by him in the opossum. It 

 seems clear that these parasites are not specific to any particular host. 



