136 A Manual of Veterinary Physiology. 



Vomiting. 



Vomiting amongst solipeds and ruminants is rare, and 

 I doubt whether in the former animal it should not be 

 considered rather as a pathological than a physiological 

 phenomenon. 



The reasons given why the horse cannot vomit are 

 various : (1) The thickened and contracted cardiac extremity 

 of the oesophagus ; (2) the oblique manner in which this 

 latter enters the gastric walls ; (3) the dilated pylorus lies 

 close to the contracted cardia, so that compression of the 

 stomach contents forces them into the duodenum ; (4) the 

 cuticular coat is thrown into folds over the opening of 

 the cardia; (5) encircling the cardia are muscular loops 

 the contraction of which keeps the opening tightly closed : 

 (6) the stomach is not in contact with the abdominal wall. 

 All these and other reasons have been assigned as the 

 cause of non- vomiting in the horse ; yet on turning to 

 ruminants, which normally do not vomit, we find these 

 conditions reversed. The stomach or stomachs and oeso- 

 phagus freely communicate, the largest stomach lies in 

 contact with the abdominal wall, the cardia is freely open, 

 the oesophagus of great size, and, still stranger, the animal 

 has the ability under the control of the will to bring up 

 food from the stomach as a normal condition, and yet no 

 vomiting occurs. 



It is evident, therefore, that all these theories are not 

 sufficiently satisfactory to account for the absence of vomit- 

 ing, and we are bound to suppose that the vomiting centres 

 in the medulla of both horse and ox, are either only rudi- 

 mentary or very insensitive to ordinary impressions. 



Vomition in the horse is no doubt seriously Interfered 

 with by the thickened cardia and the arrangemenl of the 

 muscular fibres; the folds of mucous membrane filling up 

 the orifice I do not think could offer a serious obstruction 

 to a distended stomach, for wo know that even when this 

 membrane is dissected away post-mortem, a Stomach will 

 burst, rather than allow iluid or air to be forced from the 



