ACNIDOSPORIDIA, SARCOSPORIDIA 



447 



spores themselves are capable of fission. The host muscle fiber 

 harboring the trophozoite, may vary in size from microscopic to 

 as large as 5 centimeters (Fig. 204). They are cylindrical with 

 more or less pointed extremities and with a somewhat lobulated 

 surface, and opaque whitish. They were formerly called Miesch- 

 er's tubes (Fig. 204). 



Muscle layer 

 Connective tissue layer 



Fibrous zone 



External "j 



Median > Cyst membrane 

 Internal j 



Sporoblasts 



Spores 



Fig. 205. Portion of a cyst of Sarcocystis tenella in sheep, X about 

 1000 (Alexeieff). 



As to the pathogenic effect of the parasites upon the host ani- 

 mal, fatal cases are not uncommon. In heavily infected animals 

 extensive muscular degeneration appears and the hosts die, soon 

 or later, from the infection. One peculiarity of the Sarcosporidia 

 is that these organisms contain certain toxin, sarcocystine, and 

 which when injected is highly toxic to other animals. 



Genus Sarcocystis Lankester. In muscles of vertebrates; nu- 

 merous species have been described from various mammals on the 

 basis of difference in host species and slight difference in dimen- 

 sions of spore. They are, however, morphologically indistinguish- 

 able from one another. 



S. lindemanni (Rivolta). In man; rare; in muscle fibers of 



