4<iO VOMITING. [Boon n. 



a thick fluid condition somewhal resembling pea soup and often 

 called chyme, to strain off this more fluid part into the duodenum, 

 and to submit the remaining still solid pieces to the further action 

 of the gastric juice. 



As digestion proceeds, more and more material leaves the 

 stomach, which is thus gradually emptied, the last portions which 

 arc carried through being those parts of the food which are least 

 digestible, and any wholly indigestible foreign bodies which happen 

 to have been swallowed; the latter may perhaps never leave the 

 stomach at all. The presence of food leads to the development of 

 (lie movements: but evidently it is not the mere mechanical 

 repletion of the oigan which is the cause of the movements, since 

 the stomach is fullest at the beginning when the movements are 

 slight, and becomes emptier as they grow more forcible. The 

 one tiling which does increase jmri p<t**n with the movements 

 is the acidity, which is at a minimum when the (generally alkaline) 

 food has been swallowed, and increases steadily onwards. It has 

 not however been definitely shewn that the increasing acidity is 

 the efficient stimulus, giving rise to the movements. 



The movements of even a full stomach are said to cease during 

 sleep. The nervous mechanism of the gastric movements had 

 better lie considered in connection with that of the intestinal 

 movements. 



272 Voinititir/. In a conseious individu il this act is preceded 

 by feelings of nausea, during which a copious Mow of saliva into the 

 mouth takes pl.-ire. This being swallowed carries down with it a 

 certain quantity of air, the presence of which in the stomach, 

 by assisting in- the opening of the cardiac sphincter, subsequently 

 facilitates the discharge of the gastric contents. The nausea is 

 generally succeeded at first by ineffectual retching in which a deep 

 inspiraiory effort is made, so that the diaphragm is thrust down as 

 low as possible against the stomach, the lower ribs being at 

 the same time forcibly drawn in ; since during this inspiratory 

 effort the glottis is kept closed, no air can enter into the lungs; 

 but some is drawn into the pharynx, and thence probably descends 

 by a swallowing action into the stomach. When retching passes 

 on to actual vomiting this inspiratory effort is succeeded by a 

 sudden violent expiratory contraction of the abdominal walls, the 

 glottis still being closed, so that the whole force of the effort is 

 spent, as we shall see it is in defecation, in pressure on the 

 abdominal contents. The stomach is therefore forcibly compressed 

 from without. At the same time, or rather immediately before 

 the expiratory effort, by a contraction of its longitudinal fibres 

 the oesophagus is shortened and the cardiac orifice of the stomach 

 brought close under the diaphragm, while apparently by an 

 inhibition of the circular sphincter, aided perhaps by a contraction 

 of the fibres which radiate from the end of the oesophagus over 

 the stomach, the cardiac orifice, which is normally closed, is 



