THE VITAL AND PHYSICAL FORCES. 
743 
all excited by a peculiar cause, the transmission of an electric current along the 
sensory nerves, through which these modes of consciousness are respectively excited. 
This production of muscular contraction on the one hand, and of various forms of 
sensation on the other, by the transmission of an electric current through a nerve- 
trunk, along a short distance only, appear to indicate that it is to the nervous force 
called into activity by the electric, and not to the electric force itself, that the phe- 
nomena are immediately due; and so strong an analogy presents itself between this 
development of nerve-force in a nerve, and the development of the magnetic force in 
a piece of iron, as the immediate and direct result of a certain application of the 
electric current, that, whatever may be the view taken of the relation of the magnetic 
force to the electric, tlie relation of the nervous force to the electric can scarcely 
but be placed in the same category. It is no objection to this view to say, that 
the nervous force can only be excited in the nerve of a living animal, or in that 
of an animal recently killed. In all instances of conversion of force, as already no- 
ticed, some form of matter is required as the medium of the metamorphosis; and a 
slight change in the condition of that matter may have a very considerable effect in 
modifying the process of conversion. Thus, it is by causing an electric current to 
circulate around a bar of iron, that we most readily develope the magnetic force ; 
but the molecular condition of that iron, whether hard or soft, crystalline or fibrous, 
has an important influence upon the result. Now we know that the normal condi- 
tion of the nerve-fibre can only be kept up by the continual performance of the 
changes which constitute nutrition ; so that if these changes be interrupted, its mo- 
lecular condition speedily undergoes alteration. Hence, the fact that the electric 
force can no longer call forth the manifestations of nervous force, when a short time 
has elapsed after the suspension of the nutritive processes by the stoppage of the 
circulation, is in no way inconsistent with the idea here advocated of the intimate 
relation between the two. 
In order to complete the idea of “ correlation,” however, it must be shown that tlie 
nervous force maybe the means of developing electricity; and it seems the only 
feasible method of accounting for the results of the experiments of Davy, Faraday, 
Matteucci, and others, upon the Electric Fishes, to look upon the development of 
electricity as the result of the action of their nervous force upon the peculiar organic 
apparatus to which its production is attributed. For the electric power has been 
ascertained to be entirely dependent upon the connection of that apparatus with 
the nervous centres, by nerve-trunks of large size, whose branches are distributed 
with extraordinary minuteness through the ultimate subdivisions of the electric or- 
gans ; if these nerves be wholly divided, the electric discharge can no longer be called 
forth in the usual mode; if they be partially divided, the electric power is propor- 
tionably weakened ; if the “ electric lobe” of the encephalon be destroyed, removed, 
or injured, the electric power is annihilated or weakened, in precise accordance with 
the degree of damage inflicted; vvhilst, on the other hand, if the “ eleotric lobe” be 
