40 THE FUNCTIONS OP LIFE. 



we have ourselves experienced that we ascribe similar feel- 

 ings to other sentient beings, and that we infer their existence 

 from the phenomena which they present. Wherever these 

 indications of feeling are most distinct, we find that they 

 result from a particular organization, and from the affections 

 of a peculiar part of that organization denominated the ner- 

 vous substance. The name of brain is given to a particular 

 mass of this substance placed in the interior of the body, 

 where it is carefully protected from injury. 



The sensations, for exciting which the brain is the mate- 

 rial instrument, or immediate organ, are the result of cer- 

 tain impressions made on particular parts of the body, and 

 conveyed to that organ by the medium of filaments, com- 

 posed 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 ex- 

 ternal objects, by which its activity is to be excited, and on 

 which it is to be dependent for the elements of all its af- 

 fections, both of sensation and of intellect. A considerable 

 portion of this treatise will be occupied with the develop- 

 ment of the series of means by which impressions from ex- 

 ternal objects are made on the appropriate organs that are 

 provided to receive and collect them, so as not only to give 

 rise to varied sensations, but also to convey a knowledge of 

 the existence and different qualities of the objects that pro- 

 duce them. This latter faculty is termed Perception. 



But in the formation of animals it was not the intention 

 of Providence to endow them with the mere capacity of 

 being affected by surrounding objects, and of deriving from 

 them various sensations of pleasure and of pain, without 

 granting them the power of controlling these effects, and of 

 acting on those objects in return. The faculties of sensation 

 and perception, in beings destined to be merely passive, 

 and the sport of every contingent agency, would have been 

 not merely useless, but even baneful endowments. The same 

 beneficent power which has conferred these gifts has con- 

 joined that of voluntary motion, by which the animal may 

 not only obtain possession of such objects as minister to its 



