124 MANUAL OF PHYSIOLOGY. 



wall, which aids in opening the cardiac orifice while it keeps the 

 pylorus firmly closed. 



The act of vomiting is commonly preceded by (1) a feeling of 

 sickness or nausea, (2) a great secretion of saliva, (3) retching. 

 The latter consists in a violent inspiratory effort, in the midst of 

 which the root of the tongue and larynx are raised and the rirna 

 glottidis suddenly closed so as to prevent air entering the wind- 

 pipe. The inspiratory muscles still acting, and the pharynx and 

 upper part of the oesophagus being held open, air is drawn into 

 the gullet and dilates this tube nearly as far as the opening into 

 the stomach. A contraction of the muscle fibres radiating from 

 the oesophagus over the stomach then opens the cardiac orifice 

 and allows some gas to escape. Now the act of vomiting is com- 

 pleted if at this moment the mouth and pharynx being open, 

 the larynx closed, the oesophagus on the stretch, the cardiac ori- 

 fice relaxed, and the pylorus firmly closed the expiratory mus- 

 cles forcibly contract, and, pressing upon the abdominal cavity, 

 give a sudden stroke to its contents so as to empty the stomach. 

 The wall of the stomach also contracts evenly throughout, but 

 not with any forcible anti-peristaltic action such as would greatly 

 aid in the operation of rapidly ejecting the vomit. The chief 

 object attained in the adult by the action of the muscular coat 

 of the stomach seems to be the relaxation of the cardiac orifice. 

 In children, when the fundus is little developed, and the fibres 

 radiating over the stomach from the oesophagus are numerous and 

 strong, the act of vomiting requires less effort on the part of the 

 respiratory muscles, the frequent puking of suckling infants being 

 accomplished by the gastric muscle alone. When the vomit is 

 emitted, the hyoidean, laryngeal and neck muscles relax, and 

 the air is forcibly driven out of the partially distended lungs so 

 as to clear away any remaining particles from the upper part of 

 the air passages. 



Vomiting is usually caused by irritation of the stomach 

 itself, and may be induced by either mechanical, electrical, 

 or chemical stimulation of the mucous membrane. In this 

 way some emetics, such as mustard, sulphate of copper, etc., 

 act. It may also be caused by intestinal irritation, as when 



