138 OUTLINES OF EQUINE ANATOMY. 



tube, to wliicli it is also attached, and after passing through 

 the pterygoid groove, where it is bound down by a liga- 

 ment, and lubricated by synovia, becomes inserted into the 

 fibrous palate, which it serves to render tense. 



The pendulous portion of the soft palate is very large in 

 the horse, and serves to close the posterior opening of the 

 fauces, except during the passage of food. Its inferior 

 margin is somewhat concave, and it consists simply of two 

 layers of mucous membrane, with an intervening glandular 

 layer. The floor of the fauces is that portion of mucous 

 membrane situated between the base of the tongue and 

 the epiglottis. Every portion of the mncous membrane of 

 the fauces presents large papillae and openings, for it is 

 surrounded by the palatine salivary glands. Its lateral 

 avails present depressions corresponding to the prominences 

 termed tonsils in the human subject. The pharynx is an 

 elongated passage of mucous membrane, into which several 

 muscles are inserted, and on which they act. Superiorly 

 the pharynx presents anteriorly the tivo posterior openings 

 of the nasal chamhers, separated by the inferior sharpened 

 margin of the vomer, closely invested by mucous mem- 

 brane ; on either side of these, and more posteriorly, are 

 elongated slit-like openings, each guarded by a cartilagi- 

 nous valve, the o][)enings of the Eustachian tubes, through 

 which air passes to the middle ears and to the guttural 

 pouches, more posteriorly the muscular walls of the 

 pharynx lie in contact superiorly with the guttural pouches. 

 Posteriorly the commencement of the esoplmgiis is the result 

 of the gradual narrowing of the cavity. The floor of the 

 pharynx is formed anteriorly by the upper surface of the 

 soft palate, posteriorly by the superior orifice of the larynx j 

 between the two is the posterior opening of the fauces. The 

 muscles of the pharynx are either constrictors or dilators. 

 Constrictors : Hyo-thyro pharijjigeus, runs from the posterior 

 23art of the heel process of os hyoides and from the thyroid 

 cornu. Thyro-pharyngeus, from the lateral part of the 

 external surface of the ala of the thyroid cartilage. Crico 

 pharyngeus, from the lateral part of ^he cricoid cartilage 

 (this muscle is directly continuous with the muscular layer 

 of the esophagus). These three muscles run upwards to 

 blend with their fellows and with each other in becoming 

 inserted into the central line of the upper surface of the 

 pharyngeal mucous membrane. Dilators : Hyo -pharyngeus, 



