228 



Retrogressive Processes. 



In pigs bristles which are swallowed may be massed together 

 in the intestine by the peristaltic movements into cylindrical bristle 

 balls; in ruminants hair which has been swallowed may form in 

 the abomasum one or more spherical felt-like bunches, and in the 

 same way remnants of plant fibres may also be compressed into 

 similar balls here {piUconcrcniciits, phytoconcrements, bezoars). 



Fig. 41. 

 Cut surface of half of an enterolith from horse (one-half reduced). 



Pus concretions result from the inspissation of pus retained in 

 old abscesses and other places, possibly with more or less calcifica- 

 tion. In the air chambers of horses they are met quite commonly, 

 supposed to be due to the compression of thick streptococcus pus 

 by muscular pressure (movements of chewing and swallowing), 

 often into chestnut-like or potato-like masses. In cattle tubercu- 

 lous caseated masses in bronchiectatic cavities may form hard 

 lumps, perhaps reaching the size of a fist. 



