APPLIED PHYSIOLOGY 



of the view that some of the nitrogen may also be 

 derived from the blood. This has important bearings 

 on the subject of gastric flatulence. 



The Physiology of Vomiting-. 



The act of vomiting is preceded by an abundant flow 

 of saliva, which, along with air, is swallowed. There 

 follows a series of spasmodic contractions of the dia- 

 phragm, during which the entrance to the larynx re- 

 mains closed, so that the air is forced into the stomach. 

 Thus the intra-abdominal pressure is raised, whilst that 

 in the thorax is lowered. The cardiac orifice then opens, 

 and the oesophagus is shortened by contraction of its 

 longitudinal fibres. 



Meanwhile, as observations with the X-rays have 

 shown, the cavity of the stomach itself, after the 

 development of a series of strong waves of peristalsis, 

 becomes separated into two parts by a constriction at 

 the entrance to the antrum (see Fig. 16), the cardiac 

 portion relaxes, and the contents of the fundus are 

 forced up by the pressure brought to bear upon them by 

 the diaphragm and abdominal wall (see p. 242). Occa- 

 sionally antiperistaltic waves occur from the pylorus 

 towards the cardia. 



The stomach, therefore, does not play an entirely 

 passive role in the act of vomiting, and one can easily 

 understand how, for example, sutures in its wall might 

 be torn out in the course of the act. That it is able, 

 even by its own contraction, to empty itself of its con- 

 tents is shown, too, by the possibility of vomiting taking 



