VOMITING. 149 



minute dose of tartar emetic causes active efforts to clear 

 the stomach in the human subject, in the dog, pig, and other 

 creatures, whereas large quantities are taken by the horse 

 without indicating the slightest effect. Even the most re- 

 fractory nervous system is, however, liable to be acted on 

 by some emetics, and the tincture of white hellebore injected 

 into the blood-vessels produces even in the horse symptoms 

 of nausea and spasmodic, but ineffectual eiforts for the 

 discharge of the stomach's contents. 



Before further entering on the question why the horse 

 rarely vomits, I may describe this act in animals in which it 

 occurs freely. The first symptom is the expansion of the 

 chest, drawing air into the lungs so as to fix the ribs and 

 enable the diaphragm to act from them. Then the muscles 

 of the belly act, and at the same time the neck is shortened, 

 its muscles grow rigid, there is a regurgitation in the gullet 

 and ejection through the open mouth. It is found that the 

 fluids usually secreted in moderate quantity in the throat, 

 increase in quantity under the influence of the emetic, and it 

 is probable that this is destined to favor the ejection of 

 materials thrown up from the stomach. When the normal 

 contents of the stomach have been dislodged, and vomiting- 

 continues, bile, and even stercoral matters are thrown up, 

 proving that the antiperistaltic movement extends even be- 

 yond the pylorus along the intestinal tube. The action of 

 the stomach, though not essential to the act of vomiting, 

 tends to close the pylorus, and this favors the pressure of 

 the contents against the open gullet. It is very remark- 

 able how slight the contraction of the stomach is in vomit- 

 ing, and Francis Bayle demonstrated in 1681, that if a finger 

 is introduced in the stomach of a dog during the act of regur- 

 gitation, there is no perceptible effort noticed on the part of 

 the organ; moreover, if the muscles of the belly are ren- 



