No. 3.] 



A STUDY IIV FOOT STRUCTURE. 



ZO? 



in forward reach is under severe leverage. Tliis extra leverage 

 the outside of the foot bears chiefly. In adaptation to this the 

 following structures are noted, {a) ^ The pisiform holds off the 

 flexor muscles of the outer digits, putting those muscles at a 

 better advantage, {b) The articular surfaces on the two sides 

 of the foot are differently arranged, and with some doubt I 

 interpret the fact as a mechanism to relieve pressure at the 

 anterior face of the carpus and to distribute it through the 

 depth of the bones. Thus the upper surfaces of the unciform 

 and its joint with metacarpal V are large arcs of small circles, 

 while the bearing surfaces of the median side of the foot are 

 nearly plane. To this advantage, too, I attribute the different 

 shape of the heads of metacarpals II and IV. II is cut squarely 

 across, while the upper surface of IV is inclined downward and 

 forward. 



(5) The bones of each carpal row were closely bound together 

 by ligaments, and in flexure move round a common axis. To 



First row carpals. 



See also Plate. 



Second row carpals. 



this fact and to the conformation of the joint surfaces the 

 accompanying diagrams furnish a key. The front face of the 

 carpus is strongly arched into an arc to which the axis of flex- 

 ure is a cord. This cord, the axis of movement, in the mid- 

 line of the foot falls far back of the anterior carpal surface. 

 The utility of the backgrowth of the magnum, and above it of 

 the scaphoid and lunar, is here made evident. Their articular 



1 The musculature of the tapir as given in Joter. Anat. and Phys., Vol. VI, is the 

 authority for this statement. Dissection of the pig's manus, and the markings of the 

 bones of this one, are the key to the arrangement of ligaments. 



