THE HAND. 



349 



THE HAND. 



As has already been stated, the hand is the essential part of the upper extremity, 

 and mobility is its main characteristic. It terminates in five digits which possess a 

 bony support or framework. In order that the fingers may perform their many com- 

 plicated movements numerous joints are inserted which necessitate a still greater 

 number of bones. The movements of the hand and fingers are accomplished not 

 only by the long flexors and extensors of the fingers and the flexors and extensors 



Radius 



Flexor carpi radialis 1 



Styloid process 



Scaphoid 

 Tuberosity of scaphoid 



Trapezium 

 Ridge on trapezium 



Trapezoi 

 Flexor carpi radiali 



Ulna 



Flexor carpi ulnaris 



Styloid process 

 Semilunar 

 Cuneiform 

 Pisiform 

 Os magnum 

 Unciform 

 Unciform process 

 Flexor carpi ulnaris 



FIG. 360. Anterior view of the bones of the carpus and metacarpus, showing insertion of the two carpal flexor 



muscles. 



of the carpus, which, as has already been shown, come down from the forearm, but 

 in addition by numerous short muscles situated in the hand itself. An especial 

 peculiarity of the human hand is the ability to oppose the thumb to the other digits. 



BONES OF THE HAND. 



The carpus contains 8 bones, the metacarpus 5, the phalanges 14; 27 bones in all. 



The Carpal Bones. The carpal bones are in two rows. The upper row is 

 convex above and the lower row is convex below. 



The upper row, beginning on the radial side, is composed of the navicular 

 {scaphoid}, lunate, cuneiform, and pisiform. The three first-named articulate with 

 the radius and triangular cartilage, forming the radiocarpal joint, but the pisiform 

 is separate. It is perched on the cuneiform bone and is practically a sesamoid bone 



