EAMARCK’S THEORY OF DESCENT 315 
wants which they have created have given for a long 
period, as also to others of its race, the habit of 
browsing on grass, only walks on the ground, and is 
obliged to rest there on its four feet the greater part 
of its life, moving about very little, or only to a mod- 
erate extent. The considerable time which this sort 
of creature is obliged to spend each day to fill itself 
with the only kind of food which it requires, leads it 
to move about very little, so that it uses its legs only 
to stand on the ground, to walk, or run, and they 
never serve to seize hold of or to climb trees. 
“From this habit of daily consuming great amounts 
of food which distend the organs which receive it, and 
of only moving about to a limited extent, it has re- 
sulted that the bodies of these animals are thick, 
clumsy, and massive, and have acquired a very great 
volume, as we see in elephants, rhinoceroses, oxen, 
buffaloes, horses, etc. 
“The habit of standing upright on their four feet 
during the greater part of the day to browse has 
given origin to a thick hoof which envelops the ex- 
tremity of the digits of their feet; and as their toes 
are not trained to make any movement, and because 
they have served no other use than as supports, as 
also the rest of the leg, the most of them are short, 
are reduced in size, and even have ended by totally 
disappearing. Thus in the pachyderms, some have 
five toes enveloped in horn, and consequently their 
foot is divided into five parts; others have only four, 
and still others only three. But in the rusmdznants, 
which seem to be the most ancient of mammals, 
which are limited only to standing on the ground, 
there are only two digits on each foot, and only a 
single one is to be found in the sofzpedes (the horse, 
the ass). 
‘“‘ Moreover, among these herbivorous animals, and 
especially among the ruminants, it has been found 
that from the circumstances of the desert countries 
