'/'//A' HI 'I. ID AND NECK. 63 



The posterior auricular artery arises high. You will find it behind the 

 parotid gland. Trace it very close to the ear ; between the ear and the mastoid 

 process of the temporal bone. 



The superficial temporal arteries are in the superficial fascia covering the 

 temporal muscle. They are attended by the sensory auriculo-temporal branches 

 of the fifth cranial nerve. Note the deep temporal vein piercing the temporal 

 fascia above the zygoma. (Fig. 18.) 



The ascending pharyngeal you will find buried in connective tissue, lying 

 between the internal and external carotid arteries. It arises from the external 

 carotid near the bifurcation. It is the smallest branch of the external carotid. 

 It is distributed to the pharynx and meninges. 



The internal maxillary will be dissected with the muscles of mastication 

 and the fifth cranial nerve. (Fig. 51.) 



The Hypoglossal Nerve (Fig. 31). Find this nerve crossing the internal 

 and external carotid arteries a little above the bifurcation of the common carotid 

 artery. Note that this nerve lies a little distance above the lingual artery ; that 

 the artery crosses behind the hyo-glossus muscle, the nerve in front of the 

 muscle. The nerve gives off the following branches : 



1. To the thyro-hyoid muscle. 



2. To the stylo-glossus muscle. 



3. To the hyo-glossus muscle. 



4. To the genio-hyoid muscle. 



5. To the genio-hyo-glossus muscle. 



6. To the sterno-hyoid muscle. 



7. To the omo-hyoid muscle. 



8. To the sterno-thyroid muscle. 



9. To the meninges ; recurrent branches. 



All these branches, except the meningeals, you can readily trace out. This 

 nerve must not be mistaken for the superior laryngeal branch of the pneumo- 

 gastric. Now compare the two nerves in their relation to the carotid arteries on 

 your dissection. The result of section of this nerve will be considered when 

 you dissect the tongue and outline its complete nerve-supply. 



Dissect the following muscles (Fig. 35) : 



1. The digastric and its intermediary tendon. 



2. The stylo-hyoid muscle. 



3. The mylo-hyoid muscle. 



4. The hyo-glossus muscle. 



I. Find the insertion of the stylo-hyoid muscle into the lower border of the 

 body of the hyoid bone at the junction of the greater cornu and body of the 

 hyoid bone. Study the relation of the intermediary tendon of the digastric to 

 the aponeurosis of the stylo-hyoid muscle. Trace the origin of the stylo-hyoid 

 muscle to the base and outer surface of the styloid process of the temporal bone. 



The Digastric has an anterior belly, that lies on the mylo-hyoid muscle, a 

 posterior belly, that lies under the stylo-hyoid muscle just found, an intermediary 

 tendon, and a suprahyoid aponeurosis. Carefully detach the anterior belly of 

 the digastric muscle from the digastric fossa of the mandible, and as you pull 

 this detached belly down, divide the connective tissue between this and the mylo- 

 hyoid muscle. Notice the nerve-supply to the anterior belly of the digastric 

 the mylo-hyoid branch of the inferior dental. The mylo-hyoid muscle is now 

 in full view since you removed the anterior belly of the digastric muscle. It 

 forms the floor of the mouth. It arises from the internal oblique line or mylo- 

 hyoid ridge on the inner surface of the body of the inferior maxilla. It is in- 

 serted into the mid-line of the neck into its fellow of the opposite side. This 

 muscle will be studied when you dissect the mouth and tongue. 



