Influence of circumstances on the Actions of Animals, 1059 
head. Thus the eyes of rays, both placed on the superior face, are 
rendered symmetrical, 
Snakes which crawl on the surface of the earth, having reason 
principally to see elevated objects, or those which are above them, 
this necessity has influence on the situation of the organ of 
sight in these animals, and, in fact, it has placed the eyes in the 
lateral and superior part of the head, in position to perceive easily 
that which is above them or at their sides, but they cannot see 
that which is above them or but little distance in front. Now, 
forced to make up for the lack of sight in recognizing objects which 
are before them, and which might hurt them in advancing, they 
have been able to feel these objects only by aid of their tongue, : 
which has obliged them to stretch it out with all their might. 
This habit has not only contributed to render this tongue thin, 
very long, and very contractile, but further, has forced it to divide 
itself, in a great number of species, to feel several objects at a time ; 
it has formed an opening at the extremity of their muzzle, to pass 
without being obliged to open the jaws. 
Nothing is more remarkable than the production of habits in 
herbivorous mammals. The quadrupeds to which circumstances and 
the wants which they have brought about, have given the habit of 
browsing on herbs, walk only on the earth, and find themselves 
obliged to rest on their four feet the great part of their life, execu- 
ting generally few of the ordinary movements of other Mammalia. 
The considerable time which this kind of animal is forced to employ 
every day, to replenish itself with the only kind of food which it 
uses, requires that it make little movement, that it employ only its 
eet to sustain itself on the ground, to walk or run, and that it 
never exerts itself to hang to or to grasp the trees. From this 
habit of consuming all day, great quantities of alimentative mate- 
rials which distend the organs which receive it, and of makiug only 
ordinary movements, it has resulted that the bodies of these animals 
are considerably thickened, become heavy and massive, and have 
acquired a very great volume, as one sees in the elephant, rhinoce- 
ros, cattle, buffalo, deer, ete. 
e, T A E d +L 
The habit of resting upright on thei g the greater part 
of the day to browse, has caused a thick hoof to grow, which envelope 
their toes ; and as these toes are resting without exercising any move- 
