332 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



powerful sphincteric muscle (Fig. 143). In animals, such as the car- 

 nivora and omnivora, which readily vomit, the stomach contains sub- 

 stances which are generally soft and moist and frequently finely divided, 

 and when subjected to pressure readily escape into the dilatable cardiac 

 orifice of the gullet. In herbivora which do not vomit the stomach is 

 usually filled with imperfectly divided forage, imperfectly impregnated 

 with water as compared with animal tissues and closely mixed together. 

 When these matters are subjected to pressure, the liquids which they 

 contain are pressed out and escape into the intestines through the large 



FIG. 143. STOMACH OF THE HORSE. (Colin.) 



A, cardiac extremity of the oesophagus ; B, pyloric ring. 



and generally patent pyloric orifice. Pressure, therefore, simply serves 

 to reduce the volume of the gastric contents, while small portions only 

 are separated from the mass and engage in the oesophagus, and can then 

 only move upward with great slowness. 



Vomiting is inaugurated by a special nervous impression, termed 

 nausea, which effects the combined action of the stomach, oesophagus, dia- 

 phragm, and abdominal muscles. The sensations of nausea are usually 

 accompanied by a copious secretion of saliva (by a reflex stimulation of 

 afferent fibres in the gastric branches of the vagus, the efferent nerve 



