TO THE LOWER ANIMALS 



271 



One of them, the os calcis or heel bone (ca), lies externally, 

 and sends back the large projecting heel; another, the 

 astragalus (as), rests on this by one face, and by another, 



Hctncl. 



Foot 



FIG. 18. The skeleton of the Hand and Foot of Man reduced from Dr. 

 Carter's drawings in Gray's ' Anatomy.' The hand is drawn to a 

 larger scale than the foot. The line a a in the hand indicates the 

 boundary between the carpus and the metacarpus ; b b that between 

 the latter and the proximal phalanges ; c c marks the ends of the 

 distal phalanges. The line a' a' in the foot indicates the boundary 

 between the tarsus and metatarsus ; b' b' marks that between the 

 metatarsus and the proximal phalanges ; and c' c' bounds the ends 

 of the distal phalanges ; ca, the calcaneum ; as, the astragalus ; sc, 

 the scaphoid bone in the tarsus. 



forms, with the bones of the leg, the ankle joint ; while a 

 third face, directed forwards, is separated from the three 

 inner tarsal bones of the row next the metatarsus by a 

 bone called the scaphoid (sc). 



Thus there is a fundamental difference in the structure 



