14 THE SURGICAL ANATOMY OF THE HORSE 



with the axis of the cylinder directed upwards and forwards from the 

 opening of the glottis inferiorly to the posterior nares superiorly. 



Near the nasal entrance to the pharynx is the curved slit-like 

 aperture, which represents the inferior opening of the right eustachian 

 tube. The opening is protected by a valve-like plate of cartilaginous 

 structure, the free edge ot which is directed towards the nasal chamber. 

 This opening places the pharynx into communication with the right 

 middle ear, and also with the right guttural pouch, and its position should 

 be carefully noted inasmuch as one of the methods adopted for the 

 removal of purulent matter from the pouch is by way of the eustachian 

 tube. The aperture is large enough to accommodate the little finger 

 without much difficulty. 



On the floor of the pharynx we have the opening of the glottis. 

 This is a gaping orifice placed in the centre of the floor. It is bounded 

 in front by the epiglottis, which is seen in section, and which projects 

 forwards and upwards into the pharynx, towards which its convex 

 surface is directed, its concave surface being opposed to the pendulous 

 palate. Behind the opening we have the arytenoid cartilages, the 

 inner surface of the right cartilage being represented in the plate. 

 The cut edges of the cricoid and thyroid cartilages are shown, and 

 the right side of the interior of the larynx. Very faintly marked 

 we see the upper free border of the right vocal cord, and postero- 

 inferiorly the interior of the beginning of the trachea. 



In front of the aperture of the glottis and at a slightly lower 

 level we have the isthmus of the fauces, by which the pharynx 

 communicates with the mouth ; but this aperture is practically closed 

 by the pendulous palate, which extends in a posterior direction 

 right down to the base of the epiglottis. 



Behind the rima glottidis and at a slightly higher level is the 

 entrance to the oesophagus, and this again, excepting during the 

 passage of food, is practically closed. 



The posterior wall of the pharynx presents two bulgings. These are 



