80 LABORATORY MANUAL OF HUMAN ANATOMY 



(eab) Nerve to M. biceps brachii. 



(eac) Nerve to M. brachialis. 



(eb) Lateral cutaneous nerve of forearm (N. cutaneus anti- 

 brachii lateralis), already studied. (See Fig. 24.) Note 

 the cutaneous ramus given off above the elbow to supply 

 the skin over the lateral region of the elbow. 

 Muscles. 



The muscles of the anterior compartment should now be thoroughly 

 cleaned. Study the form, position, origin, insertion, action, and inner- 

 vation of each. 



(a) Biceps muscle of upper arm (M. biceps brachii). 



(aa) Long head (caput longum}. The exact origin will be 



examined later. Observe the prolongation of the syno- 

 vial membrane of the shoulder- joint in the sulcus inter- 

 tubercularis. It is called the intertubercular mucous 

 sheath (vagina mucosa intertubercularis). 



(ab) Short head (caput breve). The insertion, the lacertus 



fibrosus, and the bursae related to the tendon of insertion 

 will be examined a little further on. 



Comparative anatomy indicates that the M. biceps 

 brachii is really a quadrigeminal muscle, coracoradial, 

 coracocubital, glenoradial, and glenocubital (Krause). 



(b) Coracobrachial muscle (M. coracobrachialis) . 



Find the bursa M. coracobrachialis. Note that the M. coraco- 

 brachialis really consists of two distinct bundles; these fuse at 

 their two extremities, but not in the middle, thus forming a 

 tunnel three centimetres long for the N. musculocutaneus. Note 

 that the M. coracobrachialis in the arm corresponds to the ad- 

 ductor system of muscles in the thigh. 



Find the fibrous arch extending from the insertion of the 

 tendon of the muscle to the inferior border of the tuberculum 

 minus (arch of Struthers). 



(c) Brachial muscle (M. brachialis) (0. T. brachialis anticus). 



How is it related to the medial and lateral bicipital sulci? 



Bend of the Elbow (Cubital Fossa). (Fig. 24.) 



Dissect in the depth between the M. brachialis and the M. 

 brachioradialis for the radial nerve and the radial recurrent 

 artery. Find the branch of the latter which perforates the sep- 

 tum intermusculare laterale to join the rete articulare cubiti, 

 thus establishing an anastomosis with the A. profunda brachii. 

 Seek the branches from the radial nerve to the M. brachioradialis 

 and the M. extensor carpi radial is longus. 



Compare the bend of the elbow with the popliteal space. 

 Study the lacertus fibrosus (0. T. semilunar fascia) carefully 

 and examine its relations. Why are these of surgical impor- 

 tance? What is the shape of the space in front of the elbow? 

 How is it bounded ? In this space examine the following : 



