88 



THE ANIMAL PARASITES OF MAN 



The relation of these parasites to certain diseases of domestic animals has been 

 studied by veterinary surgeons. Sarcosporidia may cause fatal epizootics among 

 sheep. 



There is still a wide field open for research in regard to the structure and develop- 

 ment of these parasites, and the manner in which the hosts become infected. 



The Sarcosporidia usually appear as elongate, cylindrical, or 

 fusiform bodies, rounded at both extremities and of various lengths 

 and breadths (fig. 102). In some species they may be from 16 mm. 

 to 50 mm. long, as in the sheep and roebuck. These bodies are the 

 so-called sarcocysts or Miescher's tubes. They lie in transversely 



FlG. 102. Longitudinal section of a 

 muscle of the domestic pig, with Sar~ 

 cocystis miescheriana. x 30. (After 

 Kiihn.) 



FIG. 103. Transverse section of the 

 muscle of a pig, wiih Sarcocystis 

 miescheriana. x 38. (After Kiihn.) 



striated muscular fibres which they distend more or less. The forms 

 found in the connective tissue are apparently parasites which originally 

 inhabited the muscular fibres, and only on disintegration of the fibres 

 reached the connective tissue, where they grow to large oval or globular 

 bodies (fig. 105). The mammalian muscles usually infected are those 

 of the oesophagus, larynx, diaphragm, body-wall, and the psoas muscles. 

 The skeletal muscles may be affected in acute cases, as well as those 

 of the tongue and eye. The heart muscles are sometimes parasitized. 



In fresh material cut into thin slices the parasites are frequently recognizable, even 

 with the naked eye, because of their yellowish-white colour. Under the microscope 

 they appear to be coarsely granular (fig. 103). Beginners may find some difficulty 

 in distinguishing them from other foreign bodies, such as dead and calcified encap- 

 suled Trichinae, or from Cysticerci that have died and become calcified in the early 

 stages, more particularly as the Sarcosporidia also occasionally may become calcified. 



The Sarcosporidia are always enveloped in a membrane, which 

 is probably formed at an early stage. In a few cases it remains thin 



