DR. PHILIP ON THE POWERS OF LIFE. 
373 
paper, are in the impressions it receives from the nerves of sensation, and the func- 
tions in which it cooperates with the nervous and muscular powers. Sensation and 
volition are the only sensorial powers employed in the maintenance of life. 
While the organs of the sensorial power are thus capable of more or less directly 
influencing all the other organs of the living animal ; they more or less feel in their 
turn, through the medium of the nerves of sensation, which, we have seen, convey 
an influence of wholly a different nature from that conveyed by the nerves asso- 
ciated with the organs of the nervous power properly so called, all changes effected 
in any part of our frame. By these means, this power constitutes the leading prin- 
ciple in the sensitive system, of which its organs form the central parts. 
THE organs of the nervous power properly so called, have their seat equally in the 
brain and spinal marrow, and throughout all parts of them ; and are excited, on the 
one hand, by the direct influence of the sensorial power, and on the other, by agents 
influencing the vital organs throughout every part of the frame ; all of which, as in 
the case of the impressions made on the nerves of sensation, whether existing in our 
own bodies or making their impression from without, are agents of inanimate nature. 
The immediate functions of the unaided nervous power are the excitement of the 
muscles of voluntary motion in all their functions, of the muscles of involuntary 
motion in some of their functions ; and the immediate functions of this power in co- 
operation with the muscular power and the powers of the living blood, all the powers 
of both of which are directly subjected to its influence, are the formation of the 
secreted fluids, the maintenance of animal temperature and the various more im- 
mediately assimilating functions, — namely, the functions by which, on the one hand, 
our food is converted into our various organs, and, on the other, those parts of them 
which have become useless, are separated and expelled, — which renders it necessary 
that the muscles of involuntary motion as far as they cooperate in these functions, 
which with few exceptions include the whole of these muscles, should, as we have 
seen from direct experiment is the case, be under the immediate influence of the 
nervous power. 
Neither the brain nor spinal marrow in the functions of the vital system acts through 
the other of these organs, as the brain is found to do through the spinal marrow in 
many of those of the sensitive system ; each directly influencing every part. 
The direct influence of the nervous power, it appears from what has been said, ex- 
tends to all the functions of the system with the exception of those of the sensorial 
power, which it only influences through other functions. It directly influences, and 
is directly influenced by, all the vital functions properly so called, and hence consti- 
tutes the leading principle of the system to which they belong, therefore termed the 
vital system, of which its organs form the central parts. 
THE circumstance of each of the foregoing systems being under the influence of a 
