General Principles of Physiology. 93 
perceive, that it is in vain to look for the analogies which ne- 
cessarily suggest themselves on reviewing the phenomena of 
the nervous and muscular systems. It seems to require but a 
moment’s reflection to teach every sober and unprepossessed, 
understanding, that, in our study of the sensorial power, we 
must be satisfied with observing and arranging its phenomena 
without attempting to refer them to any more general principle. 
What I am about to say of this power may be divided into 
two parts. In the first, I shall attempt by the aid of experiment, 
to draw a correct line of distinction between the sensorial and 
nervous functions; and in the second, by the same means, to 
trace the manner in which the former are so connected with 
both the nervous and muscular functions, as to render them 
essential to the continuance of life in the more perfect animals. 
However blended the organs of the sensorial and nervous 
powers may appear to be, we are assured that they are distinct 
organs, by the fact, that while the organs of the nervous power 
evidently reside equally in the brain and spinal marrow, those 
of the sensorial power appear to be almost wholly in man, and 
chiefly, in all the more perfect animals, confined to the former. 
It may be possible, therefore, to withdraw the power on which 
the one set of functions depends, without immediately destroy- 
ing the other, as we find we can withdraw the influence of the 
neryous from the muscular system without destroying the 
power of the latter. 
At the instant of death, it is evident that the sensorial functions 
cease. No impression is perceived, or followed by any act of 
volition. It is, however, equally evident to the physiologist, that 
the muscular power still remains. If, under these circumstances, 
the heart or muscles of voluntary motion be stimulated, they still 
possess the power of contraction, which is only lost by de- 
grees, and not till after the sensorial power has for a considerable 
lime been withdrawn. It is also evident to the physiologist, that 
some part of the nervous power still exists; for, if the nerves 
themselves, or those parts of the brain or spinal marrow from 
which they originate, be irritated, the corresponding muscles are 
thrown into action. The nerves, therefore, are still capable both 
