Etiology. 297 



Etiology. Primary acute dilatation of the stomach may be 



caused especially by the ingestion of unusually large amounts 

 of feed (ten quarts or more of oats or other feed). The stom- 

 ach cannot keep in motion and intimately mix an excessively 

 large mass of feed with the proper amount of gastric juice, 

 hence the feed remaining longer in the stomach swells and leads 

 to the formation of large amounts of gas. The disease also oc- 

 casionally appears after the ingestion of fresh hay or after- 

 math, or after pasturing on luxuriant pastures. 



In the larger number of the cases the cause lies, however, 

 not in the ingestion of too large amounts of feed, but in feed of 

 improper quality ; we particularly must mention in this respect 

 indigestible corn, corn-ears, rye, marshy hay, coarse straw, feed 

 which swells easily (bran, peas, beans) or easily form conglom- 

 erations (short-cut chaff with corn or barley-meal or bran) or 

 food which ferments easily (young, withered clover, alfalfa, 

 molasses, esparsette, beets and potatoes, grass heated by fer- 

 mentation and green feed in general, especially if the animals 

 drink much water after its ingestion.) Spoiled feed (moist, 

 mildewy oats or hay or rough feed, mash) may have a similar 

 effect. Improper food is particularly dangerous when the horse 

 has no chance to become used to it gradually, that is, if there is 

 a very sudden change of feed. Improper food is the more liable 

 to produce dilatation of the stomach the more of it is ingested. 

 The affection develops exceptionally in connection with the in- 

 gestion of too cold water (Mouquet). 



Overexertion or heavy work immediately after feeding also 

 plays an important role in the production of the disease. Even 

 proper and unobjectionable feed may cause dilatation of the 

 stomach if the horse is used for heavy work immediately after 

 feeding. This fact, known from actual observation, has been 

 explained by the experiments of Tangl and Scheune which show 

 that physical exercise prevents the emptying of the horse's 

 stomach and leads to a brisk excretion of water into the stomach. 



Certain anomalies of the teeth, which prevent the breaking 

 up of the food stuffs, without however causing a diminution of 

 ingestion, sometimes also cause the insufficiently masticated feed 

 to remain in the stomach for a longer time and to ferment. 



The fact that some horses are more predisposed to the af- 

 fection than others may be explained by a variability in the 

 functional capacity of the gastric muscularis. 



Dilatation of the stomach is frequently seen as a secondary 

 affection to certain intestinal diseases. Obstruction of the small 

 intestines leads the more rapidly to dilatation of the stomach 

 the nearer the obstruction is to the stomach. Not uncommonly 

 dilatation of the stomach is secondary to displacements, obsti- 

 pation and bloating of the large intestine. The causes of such 

 secondary dilatations vary. Antiperistalsis occurring on vari- 

 ous occasions may force the contents of the intestines towards 



