742 
DR. CARPENTER ON THE MUTUAL RELATIONS OF 
the secreting cells, &c., have their own respective peculiarities of structure or com- 
position, whereby they are severally enabled to serve as the material substrata, through 
which the vital force is exerted in the production of the various phenomena of life. 
III. Relations of the Vital and Physical Forces. 
Having thus endeavoured to develope the fundamental relations w^hich subsist 
between all strictly Vital phenomena, by showing that a “correlation” may be traced 
among the several forces to whose agency they are attributable, it is the author’s 
purpose to inquire, whether any similar relation can be shown to exist between the 
vital and t\\Q physical forces. 
In the conduct of this inquiry, it will be advantageous to take, as our starting- 
point, a case in which the existence of such a correlation appears particularly ob- 
vious ; that, namely, of Nervous Force, the strong analogy of which to Electricity is 
admitted by all who do not believe in the identity of these two agents. The disproof 
of their identity will be found, the author believes, in the numerous experiments of 
Prof. Matteucci and others, who have failed to procure any manifestations of a 
change in the electric state of nerves, through whose agency muscular contractions 
were being most vigorously excited ; and in the well-known fact, that the conduction 
of nervous force is prevented by pressure on the nerve-trunk, or by other disorgan- 
izing changes, which do not impair its power of conducting electricity. All the facts 
which have been adduced in support of the identity of these two forces will be found 
readily explicable on the idea of their “ correlation” or mutual convertibility ; — elec- 
tricity, when acting through nerve-fibres, developing nervous force ; and nerve-force, 
when operating upon a certain special form of apparatus, developing electricity. 
This view the author purposes now to unfold in more detail ; adducing in support of 
it facts which are so well known to physiologists and electricians, that there can be 
no occasion to do more than cite them. 
1. If an electric current be made to traverse the trunk of a motor nerve for a short 
distance only, it will produce contraction of the muscles which are supplied from its 
branches. It was formerly supposed that the contraction was excited by the imme- 
diate action of the electricity upon the muscles ; but it has been clearly proved that 
the electric current need not proceed to them, its passage along the trunk for a very 
short distance being sufficient to develope the nervous force in its branches. 
2. In like manner, if the electric current be passed for a short distance only along 
a sensory nerve, it will excite in the sensoriurn the peculiar sensations ordinarily 
produced by impressions conveyed through that nerve ; that is to say, the ordinary 
tactile sensations, if the current be transmitted along a nerve of common sensation ; 
or those of sight, hearing, smell, or taste, if the current be transmitted along the 
optic, auditory, olfactive, or gustative nerves. And thus, as remarked by Muller, 
we may, by proper management, be made conscious at one and the same time of 
pricking sensations, of flashes of light, of a phosphoric odour, and of a peculiar taste ; 
