18 TOPOGKAPHICAL ANATOMY OF 



muscle springing from the axillary border and angle and the lateral 

 surface of the neck of the scapula, and ending in a strong, partly- 

 tendinous insertion into the olecranon. A small synovial bursa lies 

 underneath the insertion. 



Some of the fibres of origin of this muscle, it should be observed, 

 spring from the surface of the deltoid. 



An aponeurosis, particularly noticeable over the distal third of the 

 muscle, covers the surface of the long head of the triceps. 



Caput mediale. — This is the smallest of the three heads of the 

 triceps. From a fleshy origin from the middle of the medial surface 

 of the humerus, immediately distal to the common insertion of the 

 latissimus dorsi and teres major, the fibres converge to a double 

 insertion. One of these is to the anterior and proximal projection on 

 the medial surface of the olecranon. The second is in line with the 

 first but farther back, i.e. about midway between the two projections 

 that occur on the medial aspect of the olecranon. 



M. CAPSULARis. — If search be made between the subscapular and 

 teres major muscles immediately behind the shoulder joint, the very 

 small, narrow, and slender capsular muscle will be found. As its name 

 indicates, it is applied to the capsule of the joint, and extends from 

 the scapula just beyond the edge of the glenoid cavity to the posterior 

 surface of the humerus, a short distance distal to the head. 



N. suPRASCAPULARis. — The fairly large suprascapular nerve dis- 

 appears into the narrow interval between the subscapular and supra- 

 spinous muscles. After crossing the cranial border of the scapula, 

 branches are contributed to the supraspinous and infraspinous muscles. 



A fibrous band crosses the nerve as it bends round the border of 

 the scapula. 



Nn, subscapulaees. — Two or three slender subscapular nerves end 

 in the subscapular muscle. 



N. THORACODORSALis. — As previously noted, the thoracodorsal 

 nerve is expended in the latissimus dorsi muscle. 



N. AXILLARIS. — The axillary nerve soon leaves the present dissection 

 by sinking into a quadrilateral space bounded by the subscapular, teres 

 major, long head of the triceps, and brachial muscles. Crossing the 

 back of the shoulder joint, but separated from the joint capsule by the 

 capsular muscle to which a small branch is furnished, it supplies the 

 teres major, deltoid, teres minor, and brachiocephalic muscles, and ends 

 as the lateral cutaneous nerve of the arm (n. cutaneus brachii lateralis) 

 in the skin over the anterior part of the elbow and forearm. 



N. MUSCULOCUTANEUS. — The musculocutaneous nerve leaves the 

 more cranial part of the brachial plexus. By a connection that it 



