OKGANS OF DEGLUTITION. 127 



lid, the epiglottis, closing over it. This cartilaginous lid rests 

 on the back and lower part of the soft palate, so that when food 

 pushes up the latter, it must force the epiglottis over, though, 

 as the larynx advances against the rigid tongue, which is 

 pressing back the food, the epiglottis is necessarily pressed 

 against its base. - If, perchance, the rapid passage of food or 

 liquid into the throat leads to a particle touching the margin 

 of the larynx, the part is so sensitive as to induce a violent 

 expulsive coughing fit. 



In the horse the passage into the pharynx is narrower, 

 and hence calling for more active effort in deglutition than in 

 the ox. From the mouth being closed behind when the parts 

 are at rest, a horse will hold up his head, with an abundance 

 of fluid, and resist any act of swallowing for a long time, 

 whereas the ox is forced to swallow more readily. The pha- 

 ryngeal liquid, which I have stated as being very abundant in 

 the horse, favours very materially the act of swallowing, and 

 indeed this, in conjunction with the salivary secretion, is 

 essential in order to ensure a rapid descent of any dry sub- 

 stance to the stomach. 



A practical lesson may be learned from the necessity of 

 moisture to lubricate the gullet. In giving a ball covered 

 with dry paper, it is apt to adhere for some time in its course 

 downwards; and I shall hereafter deseribe some bad forms 

 of choking due to this circumstance. Some practitioners 

 smear the balls with grease ; whereas we recommend an ani- 

 mal being caused to swallow some water immediately after 

 the ball has been seen to pass down the neck. 



The mucous membrane of the oesophagus, covered by a 

 dense layer of protecting scales, does not secrete much, avid 

 when any substance adheres to it the muscular coat acts 

 powerfully to remove this obstruction, and by such spasmo- 

 dic action interfering with the regularity of the act we often 



