122 DISSECTION OF THE DOG 



bounded by the subscapular, teres major, and biceps muscles. It arises from 

 the coracoid process by a long, narrow, flattened tendon which crosses the 

 insertion of the subscapular muscle, and its insertion is into the crista tubercuh 

 minoris, lateral to the common tendon of the teres major and latissimus dorsi 

 muscles. 



M. TENSOR FASCIA ANTiBEACHii. — The thui tensor of the fascia of the 

 forearm hes mainly lateral to the latissimus dorsi from which it takes origin. 



The fibres of the muscle end on the olecranon of the ulna and in the fascia 

 of the forearm. 



M. TBiCEPS BBACHii. — The triangular gap between the scapula, humerus, 

 and olecranon of the ulna is occupied by the powerful triceps muscle. Two of 

 the heads — caput longum and caput mediale — can be dissected at this stage. 

 The rest of the «nuscle must be left until the lateral aspect of the arm is 

 examined. 



Caput longum. — The cleaning of the long head is facilitated by the reflection 

 of the tensor fasciae antibrachii. This head of the triceps is a thick, triangular 

 muscle, springing from the distal two-thirds of the axillary border of the scapula, 

 and ending in a strong tendon inserted into the olecranon. 



Caput mediale. — Superficially the medial head of the triceps appears as an 

 elongated muscle between the long head and the biceps, but a considerable 

 amount of the muscle is hidden beneath the long head. The origin of the 

 medial head is by one fleshy band from the crista tuberculi minoris, and by 

 another from the neck of the humerus. A common tendon attaches the long 

 and medial heads to the olecranon of the ulna, a synovial bursa intervening 

 between the tendon and the bone. 



N. STjPEASCAPTJLABis. — The large suprascapular nerve disappears into the 

 interval between the oral border of the subscapularis muscle and the supra- 

 spinatus. After crossing the oral border of the scapula, branches are contributed 

 to the supraspinous, infraspinous, teres minor, and deltoid muscles. 



Nn. stFBSCAPULAEES. — The Subscapular nerves are small in size and three 

 or four in number. They terminate in the subscapular and teres major muscles. 



N. AXiLLAEis. — The axillary nerve is of large size, and enters the triangular 

 space circumscribed by the subscapular, teres major, and coraco-brachial 

 muscles. Then, passing between the long and medial heads of the triceps, 

 it reaches the lateral aspect of the shoulder. Its branches supply the deltoid, 

 teres major and minor, and infraspinous muscles. 



N. MTJSCXTLO-cuTANErrs. — The musculo-cutaneous nerve passes distalwards 

 between the axillary artery and the coraco-brachial muscle, and then accom- 

 panies the brachial artery, lying oral to the vessel. The terminal part of the 

 nerve runs between the radius and the biceps. Branches are given to the 

 biceps, coraco-brachial, and brachial muscles. 



In the distal third of the arm a communicating branch joins the median 

 nerve, and a short distance distal to this the n. c,utaneus antibrachii lateralis arises. 



