180 MOVEMENTS OF DEGLUTITION. 



be even made to take place against the will. This may seem 

 contrary to every one's daily experience ; but it is nevertheless 

 true. The movement by which the food is carried back, 

 beneath the arch of the palate, into the pharynx, is effected by 

 the will ; but when the food has arrived there, it is laid hold of, 

 as it were, by the muscles of the pharynx, and is then carried 

 down involuntarily. It has several times happened, that a 

 feather, with which the back of the mouth was being tickled 

 to excite vomiting, having been introduced rather too far, has 

 been thus grasped by the pharynx, and has been swallowed. 

 Moreover, we cannot perform the act of swallowing, without 

 carrying something backwards upon the tongue ; and it is the 

 contact of this something, even if it be only a little saliva, 

 with the membrane lining the pharynx, that produces the 

 muscular movement in question. 



195. This action is one of the kind now denominated reflex 

 ( 430). It is produced through the nervous system ; for if 

 the nerves supplying the part be divided, it will not take 

 place. But it does not depend upon the Brain ; for it may 

 be performed after the brain has been removed, or when its 

 power has been destroyed by a blow. It is caused by the 

 conveyance to the top of the Spinal Cord, of the impression 

 made on the lining of the pharynx ; this impression, brought 

 thither through one set of nerves, excites in the spinal cord a 

 motor impulse; which, being transmitted thence through 

 another set of nerves, calls the muscles into action. 



196. This action is, therefore, necessarily connected with 

 the impression, so long as this portion of the spinal cord, and 

 the nerves proceeding from it, are capable of performing their 

 functions : and it is one of those to which we may give the 

 name of instinctive, to distinguish it from those which are 

 effected by an effort of the Will, intentionally directed to 

 accomplish a certain purpose. It may even take place without 

 the animal being aware of the contact of any substance to be 

 swallowed with the lining of the pharynx ; for there is good 

 reason to believe that when the brain has been destroyed, or 

 paralyzed by a blow, all sensibility is destroyed ; and we have 

 also sufficient reason to consider it as suspended in profound 

 sleep or apoplexy, in which states swallowing is still per- 

 formed. In the severest cases of apoplexy, however, the 

 power of swallowing is lost ; and this is a symptom of great 



