194 CARPUS. 



a sort of pulley is formed, where it sustains the os metacarpi 

 indicis. 



Os magnum, so called because it is the largest bone of the 

 carpus, is oblong, having four quadrangular sides, with a round 

 upper end, and a triangular plane one below. The round head 

 is divided by a small rising, opposite to the connexion of the 

 OS scaphoides and lunare, which together form the cavity for 

 receiving it. On the outside a short plane surface joins the os 

 magnum to the trapezoides. On the inside is a long narrow 

 concave surface where it is contiguous to the os unciforme. 

 The lower end, which sustains the metacarpal bone of the 

 middle finger, is triangular, slightly hollowed, and farther 

 advanced on the external side than on the internal, having a 

 considerable oblong depression made on the advanced outside 

 by the metacarpal bone of the fore-finger ; and generally there 

 is a small mark of the os metacarpi digiti annularis on its inter- 

 nal side. 



Os unciforme has got its name from a thin broad process 

 that stands out from it forwards into the palm, and is hollow, 

 for affording passage to the tendons of the flexors of the fingers. 

 To this process, also, the transverse ligament is fixed that binds 

 down, and defends these tendons ; and the flexor and abductor 

 muscles of the little finger have part of their origin from it. 

 The upper plane surface is small, convex, and joined with 

 the OS lunare : the external side is long and slightly convex, 

 adapted to the contiguous os magnum. The internal surface is 

 oblique, and irregularly convex, to be articulated with the 

 cuneiforme bone. The lower end is divided into two concave 

 surfaces ; the internal is joined with the metacarpal bone of 

 the little finger ; and the external one is fitted to the metacarpal 

 bone of the ring finger. 



The nature of the carpus will be best understood by studying 

 the bones placed together, in their natural order, in the two 

 rows. 



When thus placed, they compose a structure of an oblong 

 form, whose greatest length extends across (he wrist, and forms 

 a concavity in front, while it is convex posteriorly. 



