THE GLANDS OF THE HEAD. 203 



instances, sound in the horse is produced from expirations ; 

 nor does it appear that the tongue or teeth are much con- 

 cerned in the modulations of his voice. 



The pharynx is a funnel-shaped bag, having the large end 

 forward. This bag is lined with mucous membrane, upon 

 the outer side of which are well-marked muscular fibres ; 

 and is held fast against the superior and the posterior of the 

 larynx by three pairs of constricting muscles, named the 

 anterior, middle, and posterior. The first arises from the 

 OS hyoides ; the second from the thyroid cartilage ; and the 

 last from the cricoid cartilage ; and all meet their fellows 

 upon a tendinous line at the back of the pharynx. The 

 dilators of the pharynx are numerous. The hyo pharyngeus 

 SUPERIOR arises from the inner side of the large horn of the 

 OS hyoides ; and goes to the posterior of the bag. Hyo pha- 

 ryngeus INFERIOR springs from the lower part of the large 

 horn of the os hyoides ; and goes to the posterior of the bag. 

 One of these muscles pulls upw^ard the others, sideways and 

 downward. The tensor palati arises from the styloid pro- 

 cess of the petrous temporal bone ; and, passing over a syno- 

 vial pulley on the pterygoid bone, is inserted, by expanded 

 tendon, into the anterior of the bag of the pharynx. Stylo 

 pharyngeus. From the styloid process of the petrous tem- 

 poral bone. To the most anterior part of the pharyngeal bag. 

 This last is a single muscle. 



The dilators are excited into immediate action by the 

 pressure of the morsel against the velum palati ; and then 

 pulling all at the same time, and in different directions, they 

 hold the bag of the pharynx open ; and when the food has 

 entered these muscles relax, and the constrictors one after 

 the other come into action, thus compelling the morsel into 

 the cesophagus. 



the glands of the head. 



These are mucous and salivary, with the glandular sub- 

 stance that secretes the w^ax of the ears. The salivary 

 glands secrete the fluid we call saliva ; and are three upon 

 each side of the head, the parotid, the submaxillary, and 

 the sublingual. The parotid {Plate 11. 14) is a considerable 

 body ; situated upon each side, in the hollow formed by the 

 articulation of the head with the neck, stretching around 



