Dissection of Sheep^s Head, 229 



the track of the cervico-facial branch of the Seventh nerve, but 

 leaving the nerve in situ. In so doing, a branch of the 

 external jugular vein will be cut across, lying internal, 

 and almost at right angles to this cervico-facial nerve : 

 but the external carotid artery which lies in the same direction 

 as the vein, only a quarter of an inch deeper, should if possible 

 be kept in situ running between the posterior belly of the 

 Digastric muscle and the Stylo-hyal bone. The head and 

 proximal processes of this bone should be cleaned, and the bone 

 exposed (freed from fat only) throughout its length. Within 

 half an inch of the inferior extremity of the stylohyal bone 

 will be seen the origin of the Stylo-glossus muscle, which extends 

 forwards along the under surface of the tongue as far as the 

 tip, and on whose external surface the Submaxillary plexus 

 and the course of the Gustatory nerves have been exposed : 

 the Whartonian duct has been shewn to run along its 

 inferior margin. 



The long tendon of the Stylo-hyoid muscle proceeding from 

 the posterior apophysis at the superior extremity of the Stylo_ 

 hyal bone will be now readily seen, and the inferior attach, 

 ment of the muscle to the base of the Thyroid cornua may be 

 traced, out. 



Immediately above the origin of the tendon of the Stylo- 

 hyoid muscle may be seen the insertion of the short triangular 

 Masto-styloid* muscle, which arises from the paroccipital 

 process, and is inserted into the inferior apophysis of the 

 hammer-shaped extremity of the Stylo-hyal bone. 



The ultimate course of the Hypoglossal nerve may be 

 next traced ; and in order to this, the Mylo-hyoid muscle 

 should be dissected quite down to the median raphe : care 

 being taken not to injure the broad nerve tract that lies in- 



* A special muscle found in the Carnivora Ruminantia and Pachydermata 

 (of Cobbold). Ci/cl. Anat. and Phys., art. Ruminantia, p. 527. 



