3 6 



PR A CT1CAL ANA TO MY. 



which you now see the musculo-spiral nerve, is called the external, or long 

 humeral head of the triceps ; the mass below the musculo-spiral groove is called 

 the internal or short humeral head. Trace the triceps muscle to its insertion, 

 into the olecranon process of the ulna. Cut the insertion of the triceps and 

 study the capsule of the elbow-joint and the olecranon fossa. 



10.. 



FIG. 253. TRICEPS BRACHIAMS, POSTERIOR ASPKCT. 



I. Long, middle, or scapular head. 2. Its tendon of origin from scapula. 3. External, or long humeral 

 head. 4. Internal, or short humeral head. 5. Common tendon. 6. Attachment to olecranon. 

 7. Anconeus. 8, 8. Upper portion of deltoid, posterior half removed. 9. Lower portion. 

 10. Supraspinatus. II. Infraspinatus. 12. Teres minor, middle portion removed. 13. Insertion 

 of teres minor into humerus. 14. Teres major. 15. Upper extremity of latissimus dorsi. 16. Supi- 

 nator longus. 17. Extensor carpi radialis longior. 18. Extensor carpi ulnaris. 19. Flexor carpi 

 ulnaris. 



Nen>-supply to the Triceps. As you dissect between the two humeral heads 

 of the triceps, notice the large number of branches given off to the muscle from 

 the musculo-spiral nerve, a branch of the posterior cord of the brachial plexus. 



1. //<m' I/KI n v origins IMS the deltoid muscle .' 



Two ; one from the lower lip of the scapular spine and acromion, another from 

 the outer one-third of the clavicle. (Fig. 252.) 



2. The origin of the deltoid, then, inav be said to correspond to the insertion of 

 what uutsclc f 



To the insertion of the trapezius, since this muscle is inserted into the upper 



