1136 PATHOGENIC PROTOZOA 



To the naked eye they appear as whitish, opaque, cylindrical bodies 

 in the muscles lying parallel to the fibres. In the sheep, Sarcocystis 

 tenella reaches a length of sixteen mm., and in the deer cysts of fifty 

 mm. are found. In structure the * ' tube ' ' is seen under the microscope 

 to be composed of many sickle-shaped spores, called Rainy 's cap- 

 sules. The tube has not a single cavity but a honey-comb or alveolar 

 structure, and the spores are found in small aggregations in the cham- 

 bers, completely walled off from one another. The tube itself has a 

 heavy striated wall, either secreted by the organism or composed of 

 altered muscle fiber of the host. The spores are sickle- or kidney- 

 shaped and vary both among themselves and with the host. They 

 contain a nucleated trophozoit, and at one pole either a clear or an 

 obliquely striated body. 



Laveran and Mesnil 6 (1899) obtained a toxin from Sarcocystis 

 tenella and named it sarcocystin. Darling, working in Panama, found 

 this organism in the biceps muscle of a negro from Barbados. Not 

 more than five human cases are known. 



8 Trop. Diseases Bull. London, 1920, 16, 96. 



