Different Animals, ce. 481 
The structure of the nerves and spinal marrow 
is very simple, compared with that of the brain. 
The last possesses a complicated and beautiful 
Organization, which we shall perhaps never un- 
derstand. In viewing the structure of the heart, 
we easily comprehend, in what manner each of 
its parts contributes to the peculiar function of 
this organ, the circulation of the blood: But 
we do not perceive how any one of the cavities, 
processes, dec, &c, of the brain contributes to 
sensation, volition, or the intellectual functions. 
Tt will not therefore be necessary for my present 
purpose to enter particularly into the consider- 
ation of the structure of the brain in man and 
still less so in the other animals, referred to this 
division. It may be proper, however, just to 
remark, that in each of the higher classes of 
animals, the brain has its peculiar characters, 
arising from the presence, or absence of certain 
parts, or-from the position’ &c°of these, and 
that M, Cuvier has specified these peculiarities.* 
The spinal marrow and fierves are of a fibrous 
structure, and the fibres of the latter, except at 
their remote extremities, are included in both 
a proper and a common coat, or sheath. 
The proportion of the brain, compared with’ 
the rest of the nervous system, varies in different 
* Anatomie Comparée. T, Il. p. 172175, 
