THE UPPER EXTREMITIES. 185 



the fingers toward an imaginary line drawn through 

 the middle finger. 



Joints of the Upper Extremity. The joints of the upper 

 extremity, with the exception of the wrist-joint, are the 

 most freely movable of any in the body, probably be- 

 cause the hand has the finest work to do and a greater 

 number of motions are required. Even the wrist has 

 much greater freedom of motion than the corresponding 

 joint in the lower extremity. 



The shoulder- joint is rather a deep joint, to allow of 

 the varied motion required, and has a capsular ligament 

 from the margin of the glenoid fossa above to the neck 

 of the humerus below. The elbow, which is a hinge 

 joint, has an anterior and a posterior ligament and 

 two lateral ligaments, as is practically the case in all such 

 joints. The wrist has several ligaments which, taken 

 together, are capsular in nature. 



Blood Supply of the Upper Extremity. The blood 

 supply of the upper extremity comes through the sub- 

 clavian artery, which, on the right, springs from the 

 innominate artery and on the left from the aortic arch. It 

 remains one trunk as far as the elbow, though different 

 names have been given to different parts. Thus, as 

 it passes over the lower border of the first rib, it becomes 

 the axillary, and at the lower border of the axilla, 

 where it starts down the arm, the brachial. At the el- 

 bow it divides into the ulnar and radial arteries. 



In its upper part the brachial artery lies internal to 

 the humerus but below it is in front of the bone. The 

 radial runs in a line from the middle of the elbow an- 

 teriorly to the inner side of the styloid process of the 

 radius and is much exposed to injury in the lower third 

 of its course, as when the hand is thrust through glass. 

 On it at the wrist the pulse is counted. It is much 

 smaller than the ulnar and winds around the outer side 

 of the thumb to the palm, where, with the deep branch 

 from the ulnar, it forms the deep palmar arch. The 

 ulnar artery passes obliquely inward to the middle of the 



