226 



Retrogressive Processes. 



The larger calculi cause distension of the passages and retention 

 of the secretion. The earthy salts of the saliva may also precipitate 

 in the mouth cavity. Mixed with desquamated epithelium and 

 oral vegetable organisms they accumulate as hard, brittle, dirty- 

 white deposits, particularly about the neck of the teeth, forming 

 the so-called tartar (common in dogs, rare in horses). 



Intestinal Calculi. Fecal Concretions. — Indigestible parts of 

 the food and earthy substances with them sometimes accumulate 

 in the large intestine in more or less compact masses, 

 which may have important consequences upon and menace the 



Fig. 39. 



Vegetable concretion from the colon of a horse. 



health of the animal. In the dog, more rarely in the cat, bone frag- 

 ments in the fecal material, forming in hard, dirty brow'n to black 

 sausage-shaped masses, and perhaps reaching the thickness of the 

 human arm, are quite likely to block up the rectum and colon and 

 cause erosion and necrotic ulcers of the mucous membrane, obstruct- 

 ing all the rest of the intestinal contents, and producing fecal 

 fistulse and rupture of the intestine. In horses concretions made up 

 of vegetable fibres are often formed in the c?ecum and colon, com- 

 pressed into ball-like clumps, sometimes attaining the size of a 

 human head, and more or less encrusted with mineral matter 

 (phytoconcrements, mixed conerements). 



