GENERAL OEGANIZATION 



761 







each parasite has a whitish aj^pearance, is cylindrical with somewhat 

 pointed ends, and has a slightly lobulated surface (Fig. 326). Each is 

 normally embedded in a muscle fibre, but this ultimately degenerates, so 

 that the parasite is left in the connective tissue. There is an enclosing 

 membrane which, in the larger forms, shows a radial striation. It is not 

 quite clear whether this membrane is formed by the parasite or by the 

 tissues. Within the membrane a thin multinucleate layer of cytoplasm 

 is sometimes supposed to be present, and this layer 

 also contains vacuoles in which uninucleate cells /^/T 



occur. In most cases it is impossible to detect 

 such a multinucleate cytoplasm, and all that can 

 be seen is a layer of uninucleate cells lying in 

 spaces in a homogeneous material which may, 

 however, be cytoplasm. This material gives rise 

 to a series of septa, which divide the bulk of the 

 parasite into a number of chambers (Fig. 327). 

 Those near the membrane contain single spherical 

 cells, and are smaller than the ones nearer the 

 centre of the parasite. The more deeply situated 

 chambers are larger and contain a number of 

 round cells, while those that are fully developed 

 contain a variable number of characteristic 

 sickle or crescent-shaped bodies usually called 

 spores. These are covered by a delicate mem- 

 brane, which cannot be compared with the re- 

 sistant covering of the spores of Microsporidiida. 

 In old parasites, the central part usually consists 

 of a space filled with free spores in various stages 

 of degeneration and granular debris. The central 

 portion is that which was first formed, and it 

 ultimately degenerates, while the parasite still 

 increases in size and produces new septa and 

 spores peripherally. 



The spores are presumably produced by 

 multiplication of the peripheral cells which 



reproduce by binary fission, while the space in which the cell lies dilates 

 to form a chamber. When a number of such cells is present, they 

 become transformed into the spores. The latter, which measure 

 from 10 to 15 microns in length, may be readily stained in dried films 

 by Romanowsky stains, but the true structure can only be made out 

 in properly fixed smears. Each is crescentic in shape, and has one 

 extremity rounded and the other pointed (Fig. 329). Towards the rounded 





Fig. 



OF 



326. — Sarcocystis 

 THE Pig. (After 



Manz, 1867.) 



A single cyst from a muscle 

 fibre, showing the striated 

 capsule and a rupture 

 thi-ough which can be seen 

 the groups of spores in the 

 chambers. 



