188 THE ANATOMY OF THE HORSE. 



pterygoid muscle, and rests s\iccessively on the guttural pouch and the 

 tensor palati muscle. It is crossed superficially by the inferior dental 

 and lingual nerves, and deeply by the clioi-da tynipani. It detaches the 

 following collateral branches : — 



1. The Inferior Dental Artery, a large branch arising from the convexity 

 of the first curve. It has already been seen entering the inferior dental 

 canal. 



2. The Tympanic Artery, the smallest of the branches here given off, 

 is detached at nearly the same point as the preceding, but from the 

 opposite side of the parent vessel. It lies beside the chorda tympani 

 nerve, and penetrates the petrous temporal bone to be distributed in the 

 tympanum, or middle ear. 



3. The Great Meningeal (spheno-spinous) Artery, a vessel of variable 

 volume detached from the upper side of the parent artery beneath the 

 inferior maxillary nerve, and entering the cranial cavity by the foramen 

 lacerum basis cranii. 



4. The Pterygoid Arteries, two or three, arising from the concavity of 

 the secotad curve. 



5. The Posterior Deep Temporal Artery, given ofi' from the upper side 

 of the parent trunk about half an inch before it enters the subsphen- 

 oidal canal. It enters the temporal muscle by passing in front of the 

 condyle of the temporal articular surface, and it communicates with the 

 masseteric division of the transverse facial artery by a slender branch 

 which passes through the corono-cond^doid notch. 



The Internal Maxillary Vein passes between the two pterygoid 

 muscles ; and crossing below the articulation of the jaw, it joins the 

 supei-ficial temporal vein to form the jugular. The junction takes place 

 in the substance of the parotid, a few lobules of the gland being inter- 

 posed between it and the termination of the external carotid arteiy. 



The Inferior Maxillary Division of the 5th Nerve (Plate 31). 

 This is a thick cord containing both sensory and motor filaments which 

 issues from the cranium by the forepart of the foramen lacerum basis 

 cranii. It passes obliquely downwards and backwards on the wall of the 

 guttural pouch, in front of the temporo-hyoideal articulation, and divides, 

 about an inch below its point of exit, into two branches of nearly equal 

 size — the inferior dental and lingual nerves. As it issues from the 

 foramen, it gives off the following branches : — 



1. The Stihzygomatic Nerve is detached from the posterior aspect of 

 the trunL It turns round behind the ai'ticulation of the jaw, and has 

 already been seen to join the 7th nerve, which it accompanies in its 

 distribution on the face. It sends a branch in company with the trans- 

 verse facial vessels. 



2. The Nerve to the Internal Pterygoid arises from the antero-inferior 

 aspect of the trunk. 



