1060 DISSECTION OF THE UPPER LIMBS. 



outer and lower borders of the latissimus dorsi, the serratus naagnus, and 

 the pectoralis major muscles. 



1. Muscles of the Back; Spinal Cord. During the first four days, while 

 the subject is lying on its face, the dissection of the back and spinal cord 

 below the level of the third cervical vertebra is to be completed. Let an 

 incision be made in the middle line from the level of the third cervical 

 vertebra to the sacrum, a second from the acromion to the spine of the 

 seventh cervical vertebra, and a third from the point where the fold of 

 the axilla meets the arm to the acromion. If the student be a begirmer, 

 let him at once dissect out the trapezius muscle in the direction of its fibres 

 (except the part of it which falls within the boundary of the dissection of 

 the head and neck), and afterwards the latissimus dorsi, following up its 

 fibres as close as possible to the tendon of insertion ; but let him not 

 reflect the skin further than is necessary to exhibit the anterior border of 

 the latissimus dorsi (p. 200). If the student be a senior, he will, previously 

 to the dissection of these muscles, also display the cutaneous branches of 

 the posterior divisions of the spinal nerves, which lie upon their surface 

 (p. 633). 



The trapezius muscle is to be divided by a vertical incision at the dis- 

 tance of two inches from its vertebral attachment, and on its deep aspect 

 the spinal accessory nerve and the superficial cervical artery are to be dis- 

 played (pp. 625 and 373). The rhomboid and levator anguli scapulas 

 muscles may then be dissected (pp. 202 and 643), and the nerve to the 

 rhomboids, reaching their deep surface from above. The latissimus dorsi 

 muscle is to be divided by means of an incision carried along its attachment 

 to the lumbar fascia from its superior border, at about three inches from its 

 vertebral attachment, downwards and outwards towards the external 

 border, leaving uncut the slips attached to the lower ribs and crest of the 

 ilium. The rhomboid muscles are also to be divided, and the posterior 

 scapular artery dissected (p. 373). The serrati postici superior and inferior 

 muscles may then be dissected, and the vertebral aponeurosis seen (pp. 233 

 and 240) ; after which a view may be obtained of the serratus magnus 

 muscle from its internal aspect (p. 207). 



The posterior serrati muscles and the vertebral aponeurosis may now be 

 divided, and the dissection of the muscles composing the erector spinae may 

 be proceeded with (p. 234). Beginning with the ilio-costalis or sacro-lumbalis 

 muscle, the student will dissect first its six or seven slips of direct insertion 

 into the lower ribs, then the slips attached to the upper ribs, constituting 

 the musculus accessorius ad ilio-costalem : he will afterwards turn the 

 muscle outwards and trace the separate heads of origin of the musculus 

 accessorius from the lower ribs into their insertions above ; and also the 

 similar origins of the ascendens cervicis muscle from the upper ribs. He 

 will next treat the longissimus dorsi muscle in the same manner, dissecting 

 first the costal insertions on its outer side, and then, having separated it 

 from the spinalis dorsi muscle (which always requires the division of a 

 tendon running between the two muscles), make out the insertions into the 

 transverse processes of the vertebrae. The issue of posterior branches of 

 spinal nerves, and of intercostal and lumbar vessels, will guide the dissector 

 to the separation of the masses of muscle (pp. 633 and 404). The con- 

 tinuation of the long muscles into the ascendens cervicis and transversalis 

 cervicis, and the origins of the trachelo-mastoid, are then to be traced 

 upwards in the neck. To see the last-named muscle, however, the splenius 

 muscle must be dissected and vertically divided ; and the complexus and 



