GENERAL PURPOSES OF NERVOUS SYSTEM. 347 
fabric of organized structure, the highest purpose of the 
Organic Life of Animals is to construct, and to maintain in a 
state fit for use, the mechanism which is to serve as the 
instrument of their Functions of Animal Life,—enabling them 
to receive sensations, and to execute spontaneous movements, 
in accordance with their instincts, emotions, or will. 
427. This mechanism consists of two kinds of structure,— 
the Nervous and Muscular,—which have entirely different 
offices to perform. The Nervous system is that which is the 
actual instrument of the Mind. Through its means, the indi- 
—_ becomes conscious of what is passing around him ; its 
are connected, in a manner we are totally unable to 
er with all his thoughts, feelings, desires, reasonings, 
and determinations ; and it communicates the influence of 
these to his muscles, exciting them to the operations which 
he determines to execute. But of itself it cannot produce 
any movement, or give rise to any action ; any more than 
the expansive force of steam could set a ‘mill in motion, 
without the machinery of the Steam-engine for it to act upon. 
The Muscular System is the apparatus by which the move- 
ments of the body are immediately accomplished ; and these 
it effects by the peculiar power it possesses of contracting 
upon the application of certain stimuli, of which Nervous” 
agency is the most powerful. 
_ 428. Although the presence of a Nervous System is the 
most distinguishing attribute of Animals, yet we do not en- 
counter it by any means universally. For among certain of 
_ those classes which possess on other grounds a title to be 
_ ranked in the Animal kingdom, it seems beyond a doubt that 
mo nervous system exists; and there are many others in 
_ which, if it be present at all, its condition is so rudimentary, 
that it can take little share in directing the general operations 
of the organism. The life of such beings, in fact, is chiefly 
__ vegetative in its nature ; their movements are not dissimilar in 
_ kind to those that we ‘witness in Plants ; and their title toa 
"place in the Animal kingdom chiefly rests upon the nature of 
ther food, and the mode in which they appropriate.it ($§ 7, 8). 
is the case with the Protozoa generally (§$ 128137), 
and i in a less degree with Zoophytes (§§ 121—127). 
* 429. In proportion as we ascend the Animal series, how- 
_ ever, we find the Nervous System presenting a greater and 
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pat aie 
