HEAD AND NECK OF THE HORSE 43 



Dissection. — The parotid gland must now be removed bit hy hit. It is 

 necessary to conduct tlie dissection in this manner in order to avoid 

 injury to the numerous structures, some of which are small, related to the 

 gland. It is further advisable to secure the various vessels and nerves 

 of the region as soon as possible, and follow them under or through the 

 gland. 



A small group of lymph glands should be looked for close to the man- 

 dibular joint. 



M. STERNOCEPHALicus. — The flattened tendon of the sterno-cephalic 

 muscle can now be completely examined. Its connection with the 

 tendon of the brachio-cephalic muscle by an aponeurotic sheet of 

 tissue should also be noted. 



M. JUGULOMANDiBULARis. — The strong jugulo-mandibular muscle 

 arises from the anterior margin of the jugular process of the occipital 

 ^ bone, runs obliquely downwards and forwards, and is inserted to the 

 posterior border of the ramus of the mandible. 



V. MAXlLLARis INTERNA. — For the sake of convenience, the internal 

 maxillary vein may be divided into two parts. The first part lies 

 within the mandible, and cannot be examined as yet. The second part 

 of the vein, now exposed, is a large vessel that makes its appearance at 

 about the junction of the middle and upper thirds of the mandibular 

 ramus. From this point it runs downwards and backwards, at first 

 nearly parallel to the border of the mandible, and afterwards over the 

 lateral surface of the jugulo-mandibular muscle. Then, by piercing the 

 parotid gland, it gains its lateral surface along which it travels to the 

 posterior ventral angle of the gland, where it unites with the external 

 maxillary vein to form the jugular. The relation of the vein to the 

 parotid is subject to considerable variation. Sometimes the passage of 

 the vein through the gland is abrupt ; at other times it is so gradual 

 that only the very end of the vessel is visible before the parotid is 

 removed. 



The tributaries of the second part of the internal maxillary vein are 

 as follows : — 



(1) V. temporalis suuperficialls, diSSitQWiiQ of the superficial temporal 

 artery, is formed by the union of the transverse facial (v. transversa 

 faciei) and anterior auricular (v. auricularis anterior) veins. The first- 

 named follows the dorsal border of the transverse facial artery. It has 

 already been noted that the anterior auricular vein is a satellite of the 

 artery of the same name, and that its terminal part is large because it 

 is joined by the superior cerebral vein, one of the efiluents of the 

 system of venous sinuses within the cranium. The superior cerebral 

 vein (v, cerebralis superior) traverses the temporal meatus and enters 



