VOMITING. 



331 



VII. VOMITING. 



By vomiting is meant the convulsive rejection of the contents of 

 the stomach through the mouth. It differs from rumination in that in 

 most cases it is a pathological and not a normal process, and that the 

 ejected matter usually escapes from the mouth, and is not again swal- 

 lowed. In certain animals, however, as in carnivorous birds and fishes, 

 vomiting constitutes the normal method by which indigestible sub- 

 stances are removed from the stomach ; thus birds readily reject the 

 contents of their crop, and the matter so rejected is often, as in the case 

 of pigeons, used for nourishing their young. 



Fish, amphibia, and reptiles 

 readily vomit through the contrac- 

 tions of their stomachs, and by 

 this means indigestible matters 

 are removed. In frogs this 

 process occurs frequentl}' in June 

 and July, and then is of less fre- 

 quent occurrence as the winter 

 approaches, and when they pass 

 into their state of hibernation in 

 January and February is entirely 

 wanting. Among mammals there 

 exists the greatest difference in 

 the degree of readiness with 

 which vomiting occurs, the car- 

 nivora and most omnivora vomit- 

 ing with the greatest readiness, 

 although the pig with difficult}' 

 empties its stomach by vomiting. 

 The monogastric herbivora vomit 

 very rarely, and then only with the greatest difficulty. This differ- 

 ence in the degree of facility with which vomiting takes place is due 

 to the formation of the stomach and the character of the aliments 

 which it contains. In mammals, which vomit readily, as Colin has 

 pointed out, the stomach is simple, and the oesophagus is inserted 

 toward the left extremity of the stomach far from the pylorus. The 

 03sophagus has thin, extensible walls, with an infundibular dilation at 

 its insertion in the stomach (Fig. 142). In animals which do not 

 vomit the stomach may be either simple or have several compartments, 

 the cardiac orifice, in the former case, being near to the pylorus, and the 

 oesophagus having thick walls with a narrow orifice of entrance into 

 the stomach, which is constantly occluded b}* the contractions of the 



FIG. 142. STOMACH OF THE DOG. (Colin.) 



A, oesophagus ; B, pylorus. 



