172 THE ANATOMY OF THE HORSE. 



branch of the external carotid, passes within the condyle of the lower 

 jaw, where it will subsequently be followed. 



Veins. — The jugular vein is formed within the substance of the 

 parotid gland, close behind the articulation of the jaw, and superficial 

 to the termination of the external carotid, a few lobules of the gland 

 separating the artery and vein. The vessels which unite to form it are 

 the superficial temporal and internal maxillary veins. It passes out 

 through the substance of the parotid, and then lies in a groove on 

 its surface, where it receives maxillo-muscular and posterior auricular 

 branches. 



The 7th Cranial Nerve (Portio dura) (Plate 28) emerges from 

 the aqueduct of Fallopius by the stylo-mastoid foramen of the petrous 

 temporal bone. It passes downwards and forwards at the inner face of 

 the parotid or within its substance ; and, turning round the inferior 

 maxilla, it reaches the face with the transverse facial vessels. In this 

 course it is crossed superficially by the posterior auricular artery, and 

 passes over the angle of division of the superficial temporal artery. As 

 it turns round the inferior maxilla it is joined by the sensory sub- 

 zygomatic branch from the inferior maxillary division of the 5th cranial 

 nerve. In this part of its course the 7th nerve detaches the following 

 branches : — 



1. The Anterior, Middle, and Posterior Auricular Nerves. — The first 

 two are given off at the stylo-mastoid foramen, and the last is detached 

 midway beneath the foramen and the edge of the ramus. The nerves 

 ascend in or beneath the parotid gland, and their distribution is given 

 at page 167. 



2. Nerves to the occipito-styloid, stylo-hyoid, digastricus (upper belly), 

 and stylo-maxillaris muscles. These are given off at the stylo-mastoid 

 foramen. 



3. The Cervical Branch, which is given off at nearly the same point 

 as the anterior auricular, but from the opposite side of the trunk. It 

 passes through the parotid, and reaches the surface of the gland (see 

 page 168). 



4. Numerous small and irregular branches to the parotid gland and 

 guttural pouch. 



The Subzygomatic Nerve (Auriculotemporal of man) is a branch of 

 the inferior maxillary division of the 5th nerve, given off at the foramen 

 lacerum basis cranii. It descends behind the capsular ligament of the 

 jaw ; and, crossing over the termination of the superficial temporal 

 artery, it joins the 7th as it turns round the ramus. It sends a branch 

 to accompany the transverse facial vessels (Plate 29). 



