638 INTESTINAL SYMPTOMS AND FUNCTIONAL DISORDERS. 



causes wliicli operate in the production of this unnatural con- 

 dition of the bowels are numerous as well as varied ; all, how- 

 ever, may be ranked — (1) As direct irritants, being chiefly 

 brought from without to operate at once on the mucous mem- 

 brane of the canal ; (2) As indirect excitants to increase 

 secretion and muscular activity, chiefly operating from within 

 the animal itself, the intestinal structures being their special 

 field of operation. 



' Of the former are all such agents as food, water, parasites, 

 mechanical and chemical irritants, together with certain local 

 tissue-changes, which, by their direct contact with the in- 

 testinal mucous membrane, produce their effects. Of the 

 latter, the chief are noxious emanations, products of general 

 and specific diseases, and other deleterious agents, which find 

 their way into the circulating fluids through other channels 

 than the alimentary canal, but which in the course of the 

 processes connected with the purification of the economy are 

 determined to the intestinal mucous membrane for elimina- 

 tion ; also all such disturbances of the circulation as ensue 

 from functional or structural changes of other and associated 

 organs, as the liver, the spleen, the pancreas, etc. To these 

 may be added the influence resulting from nervous disturb- 

 ance, often of a reflex character. 



Although agencies belonging to both these classes are met 

 with in the horse, it is probably a more frequent occurrence 

 that these are observed to act directly upon the mucous mem- 

 brane of the canal itself, having been conveyed there from 

 without in the ordinary processes of eating or drinking, than 

 that they enter by other channels, and are directed ultimately 

 to the alimentary canal, or even that they are the result of 

 local congestion following hepatic or other gland disturbance. 



Over-feeding, injudicious feeding, feeding with innutritions 

 or hurtful materials, drinking foul Avater, drinking excessively 

 of wholesome water, particularly when overworked, exhausted, 

 and exposed to cold and damp, are all, either individually or 

 variously combined, fertile sources of irritability and unnatural 

 laxity of the bowels. 



With the average specimen of the adult horse, the most 

 frequently operating cause of this irritable state of the intes- 

 tinal canal is probably injudicious and irregular dieting. All 



