SARCOSPOBIDIA 33 



Order 4. Sarcosporidia. 



Sarcosporides is the name given to certain parasites, either tubular, 

 spindle-shaped, or oval in form, which occur in the muscular structure 

 of mammals, birds and reptiles. The great majority of these are 

 found in the striated muscle-fibres and nowhere else ; but there are 

 a certain number of varieties of which the early stages only are found 

 in the striated muscle-fibres. These they destroy in the course of their 

 development and, surrounded only by the sarcolemma, they are 

 apparently retained in the interstitial connective tissue. A single 

 species, parasitic in the kangaroo, is an exception to this rule, being 

 found in the submucosa of the intestine (first stage of a parasite of 

 the unstriated muscles ?). 



The Sarcosporides, like many of the Cnidosporides, form numerous 

 spores by the agency of a brood-cell (pansporoblast). The life of the 

 parent organism does not cease with the completion of the process of 

 reproduction ; on the contrary, the parent organism continues to 

 grow and the number of spores which it produces to increase. Unlike 

 the Cnidosporides, the spores of the Sarcosporides are not enclosed 

 in shells. They are bean- or sickel-shaped ; they have one nucleus ; 

 and they are not furnished with a nematocyst. The whole organism 

 is surrounded by a membrane in which, as a rule, two distinct layers 

 are recognized, the inner layer being thin and hyaline. The outer 

 layer, which is not always very distinct but can generally be seen 

 in the later stages, is furnished with a striation running at right- 

 angles to the surface. This has been variously interpreted ; it may 

 be due to the presence either of rodlike structures or of pore-canals. 

 The latter alternative seems the more likely. 



Little is definitely known of the life-history of the Sarcosporides. 

 The species parasitic in the swine and the sheep are readily obtain- 

 able, and these should be examined. 



Sarcocystis miesclieriana (Kiihn), the Sarcosporide of swine, is 

 frequently discovered when examining the carcass for Trichinae. It 

 is found in the midriff, the intercostal muscles, and the muscles of 

 the larynx (according to Kiihn, in 98 per cent, of swine). Ostertag 

 has frequently found it in the abdominal muscles, and it may occur 

 in any of the striated muscles, including the heart. In this it differs 

 from Trichinae, which are never found in the muscular structure of 

 the heart. 



The organism should first be examined in the fresh state. A small 

 portion of the infected muscle is cut out with a fine pair of scissors 

 and examined in normal saline with a low-power lens, the cover- glass 

 being gently pressed down on to the specimen. Within single muscle- 

 fibres, rod- or spindle-shaped forms, rounded off at each end and 

 measuring f to 1 mm. in length by 0'08 to O'Ol mm. in thickness, 

 3 



