MOTIONS OF THE HAND. 211 



Circumduction is produced by a regular succession of the 

 motions described; it, therefore, does not require a specific no- 

 tice. 



Of the Partial Motions of the Hand.-~We\\ marked changes 

 of position occur between the first and second rows of the car- 

 pus: these are principally flexion and extension. Lateral in- 

 clination or abduction and adduction are extremely limited, and 

 circumduction does not exist. The motions, such as they are, 

 are confined within much narrower limits than those of the ra- 

 dio-carpal articulation, and have for their main fulcrum the 

 head of the magnum. 



The lateral articular surfaces of the several bones of the car- 

 pus, though they present the arrangement of joints, have not an 

 appreciable motion upon each other. Whatever changes of po- 

 sition happen among them, are probably so obscure that they 

 never appear, except under the influence of great and sudden 

 violence. The complexity of the mechanism of the wrist, 

 seems to have a double object in view : for ordinary circum- 

 stances of impulse and motion, the flexion and extension of the 

 first row upon the second, as a whole, is sufficient; but when a 

 great momentum is communicated to the structure, the number 

 of pieces which form it, and the variety of their shapes and mode 

 of attachment, diffuse the violence throughout the whole wrist, 

 and generaHy save it from dislocation or fracture. The fracture 

 of a single bone, excepting from gun-shot wounds, is a very un- 

 usual circumstance: I have, however, in possession a scaphoides 

 which was broken through transversely, and had probably been 

 in that state for a long time; as all appearance of inflammation, 

 at the period of my finding it, was absent, and as the fractured 

 surfaces had become highly polished by rubbing against one an- 

 other. 



-The pisiform bone moves with much freedom inwardly and 

 outwardly on the cuneiform, but its motion up and down is re- 

 sisted by the muscles which are attached to it. Owing to its 

 articular cavity being insulated, and to its own remoteness, a 

 dislocation of it, if it did occur, would interfere but little with 

 the general uses of the hand. 



The metacarpal bone of the thumb has a very free motion on 



