INTRODUCTION. Al 
therefrom resulting, that animals are capable of executing the 
innumerable movements that enter into walking and leaping, 
flight and natation. 
The muscular fibres, appropriated to digestion and the cir- 
culation, are independent of the will; they receive nerves, 
however, but the chief of them are subdivided and arranged 
in amanner which seems to have for its object their indepen- 
dence of the Me. It is only in paroxysms of the passions and 
other powerful affections of the soul, which break down these 
barriers, that the empire of the mx is perceptible, and even 
then it is almost always to disorder these vegetative functions. 
It is, also, in a state of sickness only that these functions are 
accompanied with sensations: digestion is usually performed 
unconsciously. 
The aliment divided by the jaws and teeth, or sucked up 
when liquids constitute the food, is swallowed by the muscu- 
lar movements of the hinder parts of the mouth and throat, 
and deposited in the first portions of the alimentary canal that 
is usually expanded into one or more stomachs; there it is 
penetrated with juices fitted to dissolve it. Passing thence 
through the rest of the canal, it receives other juices destined 
to complete its preparation. The parietes of the canal are 
pierced with pores which extract from this alimentary mass 
its nutritious portion; the useless residuum is rejected as ex- 
crement. 
The canal in which this first act of nutrition is performed, 
is a continuation of the skin, and is composed of similar lay- 
ers; even the fibres that encircle it are analogous to those’ 
which adhere to the internal surface of the skin, called the 
fleshy pannicle. Throughout the whole interior of this canal 
- there is a transudation which has some connexion with the cu- 
taneous perspiration, and which becomes more abundant when 
the latter is suppressed; the absorption of,the skin is even 
very analogous to that of the intestines. It is in the lowest 
order of animals that the excrements are rejected by the 
mouth, their intestines resembling a sac, with but the one 
opening. 
Even among those where the intestinal canal has two ori- 
