THE PHYSIOLOGY OF DIGESTION. 233 



ward by muscular contractions of the organ, from left to 

 right, towards the pylorus ; being, however, so turned and 

 contorted in its passage, that every portion of the insali- 

 vated mass becomes first macerated with the cuticular 

 secretion, and then receive the solvent gastric juice. It is 

 thus that a mass of matter undergoes the chymifying pro- 

 cess within the stomach, after which it is hurried onward 

 to be converted into chyle, within the intestines. 



Vomition. — A structural peculiarity in the stomach of 

 the horse remains to be noticed ; by which, in all ordinary 

 cases, the animal is denied the power of vomition. The 

 whole of the alimentary canal in that animal exhibits 

 uniformity of intention, unfavourable to vomition. The 

 soft palate closes all return of the contents of the stomach 

 by the mouth ; and consequently if vomition were to occur, 

 the rejected mass must come out by the nostrils. The next 

 structural impediment may be observed in the oesophagus ; 

 which, by having a different arrangement of its muscular 

 fibres, to that of ruminants, evidently proves that regurgita- 

 tion forms no part of the natural economy of the horse. The 

 obliquity of its insertion, the number, strength, and direc- 

 tion of its fleshy layers, must form a sufficient bar to all 

 ordinary tendency of the aliments to return. And the 

 superior resistance offered by the greater volume of mus- 

 cular fibre around the cardiac extremity, must, in all cases, 

 effectually prevent it. The dog and cat, which vomit 

 rather freely, have the muscular fibre much the thickest at 

 the pyloric orifice. Were the equine and the canine sto- 

 machs handed to a person perfectly ignorant of anatomy 

 or physiological discussion, his sense of touch would be 

 sufficient to decide the matter, so very marked and obvious 

 is the difference. Added to the above reasons, though not 

 of much force, is the circumstance of the horse's stomach 

 being situated far from the abdominal muscles ; this pre- 

 vents these last from directly acting upon the digestive 

 bag in that animal, but certainly cannot prevent their action 

 being felt through the pressure of surrounding parts. 



