ANIMAL AND VKGLTABLE PHYSIOLOGV. 
285 
which each animal belongs. The third includes all those arrange¬ 
ments which have been resorted to in order to accommod ’ Oe 
system to the consequences that follow from an indefinite in¬ 
crease in the number of each species. fourth class relates 
to that systematic economy in the plans of organization by which 
all the former objects are most effectually secured. 
“ With reference to the welfare of the individual animal, it is 
evident that, in the brute creation, the great end to be answered 
is the attainment of sensitive enjoyment. To this all the ar¬ 
rangements of the system, and all the energies of its vital powers, 
must ultimately tend. Of what value would be mere vegetative 
life to the being in whom it resides unless it were accompanied 
by the faculty of sensation, and unless the sensations thence 
arising w'ere attended with pleasure? It is only by reasoning 
analogically from feelings we have ourselves experienced that 
we ascribe similar feelings to other sentient being's, and that we 
infer their existence from the phenomena which they present. 
Wherever these indications of feeling are most distinct, w^e find 
they result from^a particular organization, and from the affection 
of a peculiar part of that organization denominated the nervous 
substance. The name of brain is given to a particular mass of 
the substance placed in the interior of the body, where it is care¬ 
fully protected from injury. The sensations, for exciting which 
the brain is the material instrument or immediate organ, are the 
result of certain impressions made on particular parts of the 
body, and conveyed to that organ by the medium of filaments, 
composed of a similar substance, and termed nerves. In this 
way, then, it has been provided that a communication shall be 
established between the sentient principle and the external object 
by which its activity is excited, and on which it is to be depend¬ 
ent for the elements of all its affections, both of sensation and 
intellect.” 
A considerable portion of the Treatise is occupied wdth the 
development of the series of means by which impressions from 
external objects are made on the appropriate organs that are pro¬ 
vided to receive and collect them. We must be brief on these 
different subjects, and those wdio wash for a more extended field 
must have recourse to the work itself. 
” Touch. 
“Touch is the most important of all the senses, inasmuch 
as it is the foundation of all our knowledge of the material 
world ; so its relative degrees of perfection establish marked dif¬ 
ferences in the intellectual sagacity of the several brutes, and 
have a considerable influence on the assignment of their proper 
station in the scale of animals. The integuments—under which 
