164 HEAD AND NECK 



triangular tendon which plays over the smooth triangle at the 

 root of the scapular spine and is inserted partly into the lower 

 and partly into the upper lip of the spine. The muscle is 

 supplied by the accessory and the third and fourth cervical 

 nerves. It draws the scapula medially and braces the shoulder 

 backwards, raises the tip of the shoulder, or depresses the 

 scapula and turns the glenoid fossa upwards according to 

 whether the intermediate, the upper, or the lower fibres are 

 mainly in action. 



Dissection. On the second day after the subject has been placed on its 

 face, the trapezius may be reflected. This must be done in conjunction 

 with the dissector of the arm. First separate the muscle from the occipital 

 bone, and then divide it about half an inch from the spines of the vertebrae. 

 The muscle can now be raised and thrown laterally towards its insertion. 

 On its deep surface the accessory nerve, the twigs of supply from the third 

 and fourth cervical nerves and the superficial cervical artery will be noticed. 

 It is the duty of the dissector of the upper limb to dissect these, but the 

 dissector of the head and neck should trace the superficial cervical artery 

 to its origin from the transversa colli. 



The attachments of the levator scapulae also must be denned. Two 

 twigs from the third and fourth cervical nerves, which lie on its surface 

 and finally enter its substance, have already been secured. Further, 

 passing downwards under cover of this muscle, the dorsal scapular nerve 

 (O.T. nerve to the rhomboids) and the descending branch (O.T. posterior 

 scapular) of the transversa colli artery will be found. Almost invariably 

 the dorsal scapular nerve gives one or two twigs to the levator scapulae. 



The levator scapulae, the rhomboids, the posterior serrati and the splenius 

 are classed as muscles of the second layer. The rhomboids and the lower 

 part of the levator belong to the dissector of the arm ; the remaining muscles 

 are the property of the dissector of the head and neck. 



Musculus Levator Scapulae. This muscle arises by four 

 slips from the posterior parts of the transverse processes of 

 the upper four cervical vertebrae. These unite to form an 

 elongated muscle which extends downwards and posteriorly to 

 be inserted into that portion of the vertebral border of the 

 scapula which is placed above the root of the spine. Its 

 nerve-supply comes from the third and fourth cervical nerves, 

 and also from the dorsal scapular nerve. 



The origin of the posterior belly of the omo-hyoid muscle 

 may now be examined. It is attached to the upper transverse 

 ligament of the scapula and the adjacent part of the superior 

 border of the bone. The transverse scapular artery (O.T. 

 suprascapular) will be noticed passing over the upper trans- 

 verse ligament whilst the suprascapular nerve traverses the 

 notch below it. 



The second day's work is now completed, and on the same day the 



