44 Veterinary Elements. 



brought back by coughing; in the third stage the bolus is 

 carried over the larynx into the gullet, and by the mus- 

 cular contractions of the walls of this tube is finally 

 ejected into the stomach. As the latter stages of swal- 

 lowing are involuntary the process known as reflex action 

 is gone through as follows: A nervous stimulus is sent 

 to the brain, the result of the presence of the bolus, and 

 a message is sent back from the brain to the muscles of 

 the pharynx and gullet directing the swallowing of the 

 bolus. A horse may swallow thirty boli in fifteen min- 

 utes if very hungry, from ten to twelve if the edge has 

 been taken off his appetite. Immediately behind the 

 mouth is the cavity already spoken of as the pharynx; 

 this cavity is common to the digestive and respiratory 

 (breathing) tracts; it has several openings into it besides 

 those already mentioned, namely, those of the Euslachian 

 tubes, which communicate with the ear, and 1he gut- 

 tural pouches, hollow cavities peculiar to the horse, 

 found at the back of the pharynx; these cavities are 

 sometimes filled with pus, and when thus may cause suf- 

 focation. The pharynx opens behind into the gullet 

 (esophagus), a long musculo- membranous tube, the en- 

 trance to which is located just above and behind the 

 larynx. This tube extends to the stomach, and its path 

 can be seen in the lieck during the passage of food or 

 medicine; it is lined with a delicate membrane, and 

 although containing a considerable number of muscular 

 fibres, and therefore elastic is not meant for, nor is it 

 improved by, the forcible passing of solid objects, such 

 as broom handles or whipstocks. At its entrance into 

 the stomach of the horse the mucous membrane is in 



