622 HUMAN ANATOMY. 



metacarpo-phalangeal joint obliquely. The lower crease corresponds to the inter- 

 phalangeal joint. The papillary ridges of the skin covering the terminal phalanges 

 assume varied curves and form patterns, — immutable and characteristic in the indi- 

 vidual, — impressions of which have been used of late years for purposes of identifica- 

 tion of criminals. 



On the dorsum of the hand the hollow at the base of the thumb (the so-called 

 "snuff-box") is bounded externally (radially) by the tendon of the extensor of the 



Fig. 597. 



f 



£ 



a 







Surface markings of right palm. 



metacarpal bone of the thumb and the short extensor, and internally by the tendon of 

 the long extensor (Fig. 582). The radial artery, a large vein, — cephalic vein of 

 the thumb (Treves), — and the inner division of the radial nerve cross this space. 

 Beneath it are the scaphoid and trapezium and the articulation between the latter 

 and the first metacarpal bone. 



The abductor indicis muscle makes a distinct fusiform prominence when the 

 thumb is adducted. The tendons of the common extensor and of the extensor of the 

 little finger and the slip connecting them may be seen. 



It should* be remembered that the "knuckles" are at each joint, the distal 

 extremities of the proximal bones entering into the articulation. 



