DEGLUTITION. 187 



Second Stage. In this stage the bolus is carried through the 

 pharynx, and, simple though this may appear, it must be Ix.nu- 

 in mind that there are other openings than the esophagus which 

 communicate with the pharynx into which the bolus might be car- 

 ried ; these are the posterior nares and the larynx. If carried into 

 the former, no danger would accrue ; but if into the latter, and it was 

 not at once expelled by the violent act of coughing which it would 

 excite, a fatal result would dpubtless ensue either immediately 

 if the bolus so blocked the larynx that no air could enter, or after a 

 longer period if it passed through and brought about the fatal 

 result by setting up inflammation' of the air-passages or lungs. 



The approximation of the base of the tongue to the soft palate 

 and the contraction of the anterior pillars of the fauces, the palato- 

 glossi, the so-called constrictors of the isthmus of the fauces, shut 

 off the pharynx from the mouth and carry the bolus backward far 

 enough to bring it within the influence of the constrictors of the 

 pharynx. An additional obstacle to the return of the bolus to 

 the mouth is the elevation and carrying backward of the hvoid 

 bone by the contraction of the posterior belly of the digastric'and 

 the stylohyoid muscles. Its entrance into the posterior nares is 

 prevented by the elevation of the soft palate caused by the action 

 of the levator palati, which is innervated by the facial, according 

 to Kirkes, or the internal branch of the spinal accessory, according 

 to Gray. The soft palate is at the same time made tense by the 

 tensor palati, supplied by a branch from the otic or Arnold's 

 ganglion ; by the contraction of the palatopharyngei muscles, which 

 form the posterior pillars of the fauces, and are supplied by the in- 

 ternal branch of the spinal accessory ; and by the raising of the 

 uvula, due to contraction of the azygos uvulae. The contracted 

 palatopharyngei do not come closely together, but what is lacking 

 in their approximation is made up by the uvula. This contraction 

 of the palatopharyngei also raises the pharynx and thus brings the 

 bolus well within it. It will be readily seen that the changes 

 just described not only result in shutting off any possible entrance 

 to the posterior nares, but also form of the soft palate and the 

 posterior pillars of the fauces, with the uvula between them, a 

 continuous surface well lubricated with mucus, and so inclined 

 as to direct the bolus in the direction which it should take to 

 reach the esophagus. 



The upper portion of the pharynx is in reality a part of the 

 respiratory rather than the alimentary apparatus, as is shown by 

 the fact that its mucous membrane is covered with ciliated epithe- 

 lium, as is also the upper surface of the soft palate. 



The bolus has still, however, to pass the opening into the 

 larynx without gaining entrance thereto. This is accomplished 

 in the following manner : As we have seen, the larynx is 

 raised in the manner described, aided by the thyrohyoid muscle, 



