THE METACARPUS, 197 



remarked, for the capsular ligaments of the first joints of the 

 fingers to be fixed to ; and both sides of these heads are flat, by 

 pressing on each other. s 



The substance of the metacarpal bones is the same with that 

 of all long bones. 



The metacarpal bones are joined above to the bones of the 

 carpus, and to each other by surfaces almost flat. These con- 

 nexions do not admit of much motion. The articulation of the 

 round heads, at their lower ends, with the cavities of the first 

 bones of the fingers, will soon be described. 



The concavity on the forepart of the metacarpal bones, and 

 the position of their basis on the arched carpus, cause them to 

 form a hollow in the palm of the hand, which is often useful 

 to us. The spaces between them lodge muscles, and their 

 small motion makes them fit supporters for the fingers to play 

 on. 



Though the ossa metacarpi so far agree, yet they may be dis- 

 tinguished from each other by the following marks : 



The metacarpal bone of the fore-finger is generally the 

 longest. Its base, which is articulated with the os trapezoides, 

 is hollow in the middle. The small ridge on the external side 

 of this oblong cavity is smaller than the one opposite to it, and 

 is made flat on the side by the trapezium. The internal ridge 

 is also smooth, and flat on its ulnar side, for its conjunction 

 with the os magnum ; immediately below which, a semicircular 

 smooth flat surface shows the articulation of this to the second 

 metacarpal bone. The back part of this base is flattened where 

 the long head of the extensor carpi radialis is inserted, and its 

 forepart is prominent where the tendon of the flexor carpi radialis 

 is fixed. The tubercle at the internal root of its head is larger 

 than the external. Its base is so firmly fixed to the bone it is 

 connected with, that it has no motion. 



The metacarpal bone of the middle finger is generally the 

 second in length ; but often it is as long as the former : some- 

 times it is longer ; and it frequently appears only to equal the 

 first by the os magnum being farther projected downwards 

 than any other bone of the wrist. Its base is a broad super- 

 17* 



