46 Evolution and Adaptation 



the limbs are put as organs of locomotion has not inter- 

 fered with an astonishing number of varieties of struc- 

 ture, adapted to different conditions of existence, such as 

 the short legs used for creeping in salamanders, lizards, 

 turtles, crocodiles ; the long and thin legs of good runners, 

 as the hoofed animals ; the mobile legs of the apes used for 

 climbing ; and the parachute legs of some squirrels used for 

 soaring. Even more striking is the great variety of hands 

 and feet, as seen in the flat, hairy foot of the bear; the 

 fore-foot of the armadillos, carrying long, sickle-shaped 

 claws ; the digging foot of the mole ; the plump foot of 

 the elephant, ending in a broad, flat pad with nails around 

 the border, and without division into fingers ; the hand of 

 man and of the apes ending with fine and delicate fingers 

 for grasping. To have discovered a general plan of struc- 

 ture running through such a great variety of forms was 

 proclaimed a triumph of anatomical study. 1 



A study of the bony structure of the limb shows that typi- 

 cally it consists of a single proximal bone (the humerus in 

 the upper arm, the femur in the thigh), followed by two 

 bones running parallel to each other (the radius and ulna in 

 the arm and the tibia and fibula in the shank); these are 

 succeeded in the arm by the two series of carpal bones, and 

 in the leg by the two series of tarsal bones, and these are 

 followed in each by five longer bones (the metacarpals and 

 metatarsals), and these again by the series of long bones 

 that lie in the fingers and toes. Despite the manifold variety 

 of forms, Fleischmann admits that both the hind- and the 

 fore-limbs are constructed on the same plan throughout the 

 vertebrates. Even forms like the camel, in which there are 

 fewer terminal bones, may be brought into the same category 

 by supposing a reduction of the bones to have taken place, 

 so that three of the digits have been lost. In the leg of 

 the pig and of the reindeer, even a greater reduction may 



1 This paragraph is a free translation of Fleischmann's text. 



