DIGESTION 231 



The swallowing reflex is started by the contact of 

 food with the back of the tongue, the superior laryn- 

 geal being the afferent and the recurrent laryngeal the 

 efferent nerve concerned. Loss of the swallowing reflex 

 always indicates a bilateral lesion, as destruction of 

 either both superior or both inferior laryngeals is neces- 

 sary to bring it about. The unstriped muscle of the 

 lower part of the oesophagus is to a large extent auto- 

 matic in its action, and independent of the nervous 

 system. Thanks to this it is still possible to introduce 

 food into the stomach even when voluntary swallowing 

 is impossible and the deglutition reflex abolished ; for 

 if a tube be passed into the upper thoracic region of the 

 oesophagus, any food introduced through it will be passed 

 on by the unstriped muscle. Advantage is taken of this 

 in ' nasal ' feeding. If the vagus nerves be divided, a 

 condition of paralytic dilatation of the oesophagus ensues, 

 and it is probable that this may also occur as the result 

 of disease affecting the nerves. That a reverse peri- 

 stalsis in the oesophagus is possible seems to be proved 

 by the occurrence of rumination in some subjects. 



Digestion in the Stomach. 



Experiments on animals, as well as the results of 

 gastrectomy on patients, have shown that the stomach 

 is not actually essential to life. On the other hand, 

 there can be no doubt that it is not really a superfluous 

 organ, but is of great use in so preparing the food as to 

 protect the intestine from possible injury. 



The uses of the stomach are apparently these : (1) To 



