82 SURGICAL ANATOMY OF THE 



of great surgical importance. The anterior border is the 

 more prominent, and is rounder than the posterior, which 

 becomes lost in the general surface of the posterior part 

 of the neck. In most works on descriptive anatomy it 

 is not sufficiently enforced that this muscle completely 

 covers in the common, internal, and external carotids, 

 and that while the muscle, its integuments, and the 

 fascial coverings are intact, it may surgically be consid- 

 ered to extend forwards as far as the angle of the jaw. 



Its pulsations are in reality felt beneath its own border, 

 or immediately beneath its sternal and clavicular at- 

 tachments. 1 



Structures superficial to the Sterno-mastoid. On re- 

 flecting the skin and cellular tissue the first structure 

 met with is the platysma, passing obliquely backwards 

 from the jaw to the shoulder, and on dissecting off this 

 layer of muscular tissue from above downwards, the 

 structures met with are, some filaments of the small oc- 

 cipital nerve, the great auricular nerve, the external 

 jugular vein, which usually crosses the muscle obliquely 

 at about its middle, to pass ultimately into the subcla- 

 vian vein, the transverse superficial cervical nerve, pass- 

 ing forwards to the under surface of the platysma and 

 integument, and some branches of the descending clavic- 

 ular nerves. The disposition of the fibres of the pla- 

 tysma, as far as regards the direction of the external 

 jugular vein, is important, as in venesection it is neces- 

 sary to cut across them, and not in their continuity, 

 otherwise the wound would close from muscular con- 



1 According to Richet it is impossible to puncture the common 

 carotid from the side of the neck without perforating the sterno- 

 mastoid in the undissected subject, a statement I have taken care 

 to verify. 



