12 Practium II. The Biceps and Brachialis. 



white cord, the ULNAR NERVE. Trace it to the elbow, where it is lodged 

 in a notch between the projecting olecranon process (PI. I) and the ulnar 

 projection of the humerns. 



a. It has the same location in man and, notwithstanding the protec- 

 tion from injury thus afforded, an unguarded blow upon this part of the 

 elbow may so far press upon the nerve as to cause the tingling and more 

 or less painful sensation known as "crazy-bone." 



b. Slit the fascia of the antibrachium and separate the muscles so as 

 to follow the nerve distad. At about the middle of the length of the anti- 

 brachium it divides into two branches of which one is distributed to the 

 palm and the other to the dorsal skin of the hand ; branches are given off 

 to the pad at the wrist joint. 



17. Division of the Triceps. Transect it at about the middle ; turn 

 the distal half away from the bone, leaving it attached for later observa- 

 tion. Cut the proximal half from the humerns and scapula. 



18. The Musculo-Cutaneous Nerve. Between the biceps and the 

 bone push first a scalpel-handle and then a finger ; then draw the muscle 

 gently from the bone and rotate it slightly. This will, expose a NERVE, 

 the MUSCULO-CUTANEOUS, which emerges from the parts about the shoul- 

 der, sends several branches to the proximal part of the biceps and then 

 continues to the elbow, passes to the radial side of the arm, and is distrib- 

 uted to-the skin ; Anatomical Technology, Fig. 103, N. Met., and 1022. 



a. Like many other nerves it supplies both muscle and skin, con- 

 taining fibers derived from both the ventral (motor or "anterior") and 

 dorsal (sensory or "posterior") spinal nerve roots ; it is a "mixed" nerve; 

 see Practicum VI, the MYEL. 



19. Origin of the Biceps. The tapering proximal end of the mus- 

 cle terminates in a single, subcylindrical tendon (sinew) which enters a 

 groove in the bone covered by a fibrous sheet ; PI. V, j, 4. Slit the sheet 

 and follow the tendon to its attachment on a slight projection of the lip of 

 the glenoid cavity of the scapula. 



a. The second tendon of origin in man from the tip of the coracoid process (whence 

 the name biceps) is absent in the cat ; PI. V. 



S 20. The Brachialis. Partly covered by the biceps and lying closely 

 against the "outer" side of the humerus is the BRACHIALIS (brachialis 

 anticus]. The distal ends of the two muscles may be followed together 

 as directed in 21. 



2i. Insertion of the Biceps. This is hidden by muscles of the 

 antibrachium arising from both sides of the humerus but especially from 

 the radial ("outer") side. These must be cutaway, though not neces- 

 sarily so far distad as in PI. V. Transect the muscles of the antibrach- 

 ium covering the insertion of the biceps at about one-third of the way 

 from the elbow to the wrist, and peel the proximal portions toward the 

 wrist, but without cutting them away at their origins. 



a. The fibrous sheath, FASCIA, covering them receives a slip of ten- 

 don from the biceps. This really constitutes a second and considerable 

 insertion of the muscle, so that, especially in the absence of the second 

 head one might well regard this muscle in the cat as a bipes rather than a 

 biceps. 



$ 22. Insertion of the Brachialis. Use the tracer as much as possible, 

 the scalpel sparingly, and ascertain that the brachialis is inserted upon 

 the ulna, while the tendon of the biceps passes between the ulna and the 



