370 A MANUAL OF ANATOMY. 



nerve through the scapular notch into the infraspinous fossa, to terminate in 

 the muscle there. 



Find the dorsalis scapulae artery and trace its course upon the back of the 

 scapula, cutting as much of the overlying muscle away as is necessary to fol- 

 low it. 



In the same way dissect out the circumflex nerve and the posterior circum- 

 flex artery to their distribution to the teres minor and deltoid muscles. 



Divide the rhomboid muscles vertically midway between their attachments 

 and reflect them. 



At the upper part of the vertebral border of the shoulder find the posterior 

 scapular artery and trace its branches as far as possible. 



Cut the latissimus dorsi transversely at its middle and reflect its central 

 portion, severing it from its costal attachments. 



The Serratus Posticus Superior. Fig. 76. 



Origin. From the lower portion of the ligamentum 

 nuchse, the spines of the last cervical and first three dorsal 

 vertebrae, and the supraspinous ligaments. 



Insertion. Into the posterior surface of the second to 

 the fifth ribs inclusive, just external to their angles. 



Nerve Supply. The second and third intercostal nerves. 



Action. To raise the ribs and aid in inspiration. 



The Serratus Posticus Inferior. Fig. 76. 



Origin. From the spines of the last two dorsal and first 

 two lumbar vertebrae. 



Insertion. Into the lower borders of the last four ribs. 



Nerve Supply. The tenth and eleventh intercostals. 



Action. To draw the ribs downward, thus affording a 

 fixed point for the action of the diaphragm and so aiding 

 inspiration. 



The Posterior Scapular Artery. Fig. 76. 



Usually arises from the third portion of the subclavian, 

 but may come off as the lower branch of the transverse 

 cervical. 



For its course from the subclavian see page 1 13. When 



