XIX] PROTOZOA CAUSING DISEASE 505 



body terminates as a pointed rigid process. A hsmatozoon 

 which, according to Lewis and Crookshank/ is identical with 

 that occurring in the healthy rat has been discovered by 

 Evans, but first assumed to be a spirillum and considered by 

 this observer as the cause of the surra disease, a deadly 

 malady affecting in India, in an epidemic form, horses, 

 mules, and camels. Crookshank " gave good photographs of 

 them ; he believes them to belong to the genus Trichomonas. 

 Lingard in his exhaustive reports to the Government of India 

 on surra disease had besides making a thorough investigation 

 into the cHnical and pathological aspects of the disease 

 described the nature of the contagion, the life-history of the 

 parasite in its relation to the various phases of the disease. 



4. Psorospermia or Cocddia. — (a) Coccidium oviforme. 

 The class of protozoa known as sporozoa — unicellular 

 parasites of fixed form of body, surrounded by a capsule, 

 forming within their body a number of spores, each sur- 

 rounded by a cuticle, the spores becoming free after the 

 bursting of the capsule, and giving rise to a new parasite — 

 comprise a group which is important to the pathologist, oval 

 psorospermia or coccidia. These are capsulated, uni- 

 nuclear, oval, protoplasmic corpuscles, in the interior of 

 which out of the protoplasm a number of spores are 

 developed ; many of these coccidia are endo-epithelial 

 parasites, and as such are the causes of a chronic 

 hypertrophy of the epithelium. The coccidium best studied 

 is the Coccidium oviforme, causing in the liver of the 

 rabbit a chronic disease of the epithelium of the bile ducts, 

 by which the bile ducts become greatly distended, their 

 epithelium much hypertrophied and their coats thickened ; 

 in consequence of this whitish-grey nodules appear in the 



^ Journal of the Roy. Micr. Society^ Nov. 10, 1S86. 

 ^ Ibidem, loc. cit. 



