THE DISSECTION OF THE BACK 161 



cutaneous) and the medial cutaneous nerve of the forearm (O.T. internal 

 cutaneous). 



The Position of the Brachial Plexus. The plexus lies in the lower and 

 anterior part of the posterior triangle of the neck, partly above and partly 

 below the posterior belly of the omo-hyoid ; posterior to the clavicle ; and 

 in the axilla. Above the clavicle it is covered by the skin, the superficial 

 fascia and the platysma, branches of the supraclavicular nerves, the first 

 layer of deep fascia, the external jugular vein, and the terminal parts of the 

 transverse cervical and transverse (supra) scapular veins ; the second 

 layer of deep cervical fascia, the transverse cervical artery, the posterior 

 belly of the omo-hyoid, the nerve to the subclavius, and the third part of 

 the subclavian artery. Behind the clavicle it is crossed superficially by 

 the transverse scapular artery (O.T. suprascapular). Below the clavicle it 

 is covered by the skin and superficial fascia, the platysma, the middle 

 supraclavicular nerves, the deep fascia, the pectoralis major, the pectoralis 

 minor, the cephalic vein, the branches of the thoraco-acromial artery, the 

 costo-coracoid membrane, and the axillary artery and vein. 



Its posterior relations in the neck are the scalenus medius and the long 

 thoracic nerve. In the axilla the serratus anterior, the fat in the interval 

 between the serratus anterior and the subscapularis, and finally the sub- 

 scapularis itself. 



After the brachial plexus has been examined, the clavicle must be 

 replaced in position and the skin flap, reflected from the posterior triangle, 

 must be replaced and fixed in position by a few sutures. 



On the ninth day after the body is brought into the room, 

 that is, on the sixth day after it has been placed on its back, 

 it will be turned upon its face, with the thorax and the pelvis 

 supported by blocks. The body will remain upon its face for 

 five days, and during that period the dissectors of the head 

 and neck must complete the dissection of the posterior part 

 of the scalp ; dissect the muscles, vessels and nerves of the 

 back and the suboccipital region ; and remove and examine 

 the spinal medulla. 



THE DISSECTION OF THE BACK. 



Dissection. Make a -median longitudinal incision from the external 

 occipital protuberance to the seventh cervical spine, and a second laterally 

 from the seventh cervical spine to the acromion, and throw the flap laterally. 

 When this has been done the posterior triangle will be exposed from behind, 

 and the dissector should take the opportunity of noting the positions of the 

 contents and the constituent parts of the floor from this aspect. Afterwards 

 he must look for the superficial nerves in the superficial fascia over the 

 upper part of the trapezius. If the great occipital nerve was not found 

 during the dissection of the scalp secure it at once, as it pierces the deep 

 fascia covering the upper end of the trapezius, about midway between the 

 external occipital protuberance and the posterior border of the mastoid 

 portion of the temporal bone ; trace it upwards through the dense superficial 

 fascia of the scalp and clean the branches of the occipital artery which are 

 distributed in the same region. The smallest occipital nerve will be found 

 VOL. II 11 



