102 



THE PARASITISM OF 



of the bile duct, which, in most places, has not preserved its typ- 

 ical cubical form, but is somewhat embryonic in character. The 

 most striking feature of the tumour, however, is the extreme com- 

 plexity of the processes projecting from the mucous coat. These 

 projections are very finely branched, and thus the characteristic 

 convoluted appearance is obtained. They carry with them a small 

 quantity of fibrous tissue, and, usually, very large thin-walled ves- 

 sels. Filling up the interstices of this adenomatous structure are 

 seen multitudes of parasites in many stages of development. Some 

 are encysted, and in this condition may be observed lying free, or 

 stilt contained within the epithelial cells of the tumour. Naked 



Fig. 49. — a, b, Coccidia occupying epithelial cells of the affected bile 

 ducts ; c, appearance presented after escape of the parasite. 



forms may be seen from the smallest homogeneous globules of 

 protoplasm, in all stages of granularity of protoplasm, according 

 to their age, up to the adult form of the encysted parasite in which 

 the protoplasmic contents of the cyst become very coarsely gran- 

 ular. These younger forms are seen usually lying embedded in 

 the epithelial layer. If an animal still suffering from the acute 

 form of the disease is examined, the crescentic spores, due to 

 "endogenous sporulation," may be seen if special precautions are 

 taken. 



If the animal recovers from the disease, the tumour just 

 described commences — apparently in a very short time — to alter 

 its appearance. Many of the parasites pass out of the body, the 

 remainder show signs of granular and fatty degeneration, their 

 cyst walls resisting longest, and being, for some time, obviously 



