186 



THE ANATOMY OF THE HORSE. 



The Inferior Dental Vein (Plate 30) has a distribution similar to 

 that of the artery which it accompanies, and it joins the internal 

 maxillary vein. 



The Inferior Dental Nerve (Plate 30) is a branch of the inferior 

 maxillary division of the 5th nerve. It accompanies the vessels in the 

 bone, supplying tlie teeth, and detaching sensory mental branches to 

 the lower lip. 



The Mylo-Hyoid Nerve (Plate 30) is a branch of the preceding nerve. 

 It descends between the internal pterygoid muscle and the bone, and 

 reaches the intermaxillary space. There it has already been dissected 

 on the surface of the mylo-hyoid muscle, to which and the lower belly of 

 the digastricus it is distributed. 



The Lingual or Gustatory Nerve (Plate 30) is a large branch of 

 the inferior maxillary division of the 5th. Between the two pterygoid 

 muscles it is joined by the chorda tympani branch of the 7th nerve, 

 and it is continued between the internal pterygoid and the bone to 

 reach the tongue. It will be followed in the dissection of that organ. 



The Internal Maxillary Vein (Plate 30) lies in front of the pre- 

 ceding nerve. It is the direct continuation of the buccal vein already 

 dissected in the cheek. It Avill subsequently be followed to its termina- 

 tion, where it forms the jugular by union with the superficial temporal 

 vein. 



The Lingual Vein (Plate 30) drains blood away from the tongue. 

 It runs in company with the gustatory nerve; and after receiving 

 branches from the soft palate and the pharynx, it joins the buccal vein 

 between the internal pterygoid muscle and the bone. 



Pterygoid Vessels. The pterygoid muscles derive their blood from 

 branches of the internal maxillary or of the inferior dental artery. 

 The inner muscle receives also the inner division of the maxillo-mus- 

 cular artery. The pterj'goid veins join the internal maxillary vein. 



Directions. — The external and internal pterygoid muscles must now 

 be removed. In cutting away the outer muscle, the thick buccal nerve 

 will be found passing through it near its origin, and giving branches to 

 the muscle. The nerve is to be preserved to show its origin. Care 

 must also be taken of the internal maxillary vessels, and of the inferior 

 maxillary nerves, which are included between the muscle and the 

 guttural pouch. The internal pterygoid is to be cut close to its origin, 

 and taken away without severing the vessels and nerves just dissected. 

 The pterygoid branch of the inferior maxillary division of the 5th nerve 

 will be found entering it, and an inch or two of the nerve should be 

 preserved to show its origin. Extending along the deep aspect of the 

 origin of the muscle is the tensor palati muscle, and care must be taken 

 not to injure it. The deep face of the internal pterygoid is related to 

 the phai'ynx, the guttural pouch, the great cornu of the hyoid bone, tlic 



