140 ANATOMY OF UPPER EXTREMITY, ETC. 



of the ulna ; between the tendon and the olecranon is a 

 synovial bursa. 



The long head of the triceps divides the triangular space 

 left between the teres major and the subscapularis muscle 

 into a smaller triangle on the outer side, and into a quad- 

 rangular space between it and the humerus on the inner 

 side. Through the small triangular space passes the dor- 

 salis scapulae artery, and through the quadrangular space 

 the posterior circumflex artery, and circumflex nerve. Be- 

 neath the belly of the triceps, and between it and the shaft 

 of the humerus, pass the musculo-spiral nerve and the supe- 

 rior profuuda artery. 



The triceps muscle must be divided in the middle, and turned up- 

 ward and downward to follow out the course of this artery and nerve. 



DISSECTION VII. 



FRONT OF THE FOREARM. 



An incision should be made down the forearm to the wrist, and 

 there joined by a short transverse one ; the skin is to be removed in 

 such a way as to permit the origin of the veins of the elbow to be 

 seen, as well as the terminations of the cutaneous nerves (p. 107). 

 The muscles of the forearm are surrounded by a firm aponeurosis, 

 which not only invests them collectively, but penetrates between them 

 individually. This aponeurosis is to be divided and removed ; toward 

 the condyles it will be found that the muscular fibres originate from 

 it, and where they do, it will necessarily be left adherent to them. 

 The muscles are best isolated from one another by commencing at the 

 tendons, and tracing their separations upward to the elbow ; the 

 sheaths of the muscles and the cellular tissue lying in their inter- 

 spaces must all be removed, and the tendons should be dissected as 

 cleanly as possible ; the beautiful appearance they present when pro- 

 perly dissected fully repays the labor spent upon them. 



The tendon of the biceps muscle divides the muscles of 

 the forearm into an external and an internal group, each 

 group being collectively attached to the condyle of the 

 humerus of its respective side by a common tendon, which 

 also sends septa between the muscles ; they are also divided 

 into a deep and a superficial layer. In separating these 

 muscles, the arteries and nerves will necessarily come into 

 view. It will be seen that the brachial artery dips down- 

 ward between the muscles, and divides into two branches, 



