DISSECTION OF THE UPPER EXTREMITY 87 



the long head of the M. biceps brachii above and of the long head 

 of the M. triceps below. 

 (e) Long head of biceps muscle (caput longum M. bicipitis brachii). 



Note its relations to the joint. Why is it of especial importance? 

 Note its exact mode of origin. While in the joint, surrounded by 

 the synovial membrane, it lies beneath a sort of inverted gutter 

 formed by the superior glenohumeral ligament and by the posterior 

 border of the coracohumeral ligament. 



[In the horse the tendon is inserted into the external surface of 

 the capsula articularis; in sheep it becomes invaginated in the 

 joint-capsule, is immediately related to the synovial membrane, 

 being swung by a meso of the latter; in higher animals and man 

 it is free in the joint. All these phylogenetic stages are repeated 

 in the ontogeny of the human embryo. (Cf. Welcker, H., Die 

 Einwanderung der Bicepssehne in das Schultergelenk, Arch. f. 

 Anat. u. Physiol., Anat. Abth., Leipzig, 1871, p. 20.)] 

 (/) Synovial membrane and its evaginations. 



Note exact extent of synovial membrane. Observe the 

 following constant evaginations: 



(fa) Subscapular bursa, in the adult usually communicating with 



the M. subscapularis (already studied). 



(fb) Vagina mucosa intertubercularis (for tendon of long head of 



biceps muscle). 

 (g) Movements of the joint. 



What muscles are concerned in the following movements? 



1. Flexion. 



2. Extension. 



3. Abduction. 



4. Adduction. 



5. Circumduction. 



6. Rotation. 



What structures check excessive movements in the directions 

 mentioned ? 



What agencies contribute to keeping the joint surfaces in con- 

 tact, i.e.) to maintaining the integrity of the joint? 



For the details of the anatomy of this and other joints, consult 

 R. Fick, Handbuch der Anatomic und Mechanik der Gelenke (in 

 Bardeleben's Handbuch), Jena, 1904. 



FOREARM AND HAND (ANTIBRACHIUM ET 



MANUS). 



Superficial Fascia of Dorsum of Hand. 



Make incisions through the skin along the margo ulnaris 

 and the margo radialis of the hand. Dissect off the skin of the 

 back of the hand (dorsum manus), detaching the flap at the roots 

 of the fingers. Make an incision along the middle line of the 

 dorsum of each digit and reflect the skin radialward and ulnar- 

 ward in each instance. Take no fat with the skin. 



