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.? 
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. 
