ELECTRIC MANIFESTATIONS OF MUSCLE AND NERVE. 345 
Electricity by its action on the electrical organs, just as it pro¬ 
duces Motion by its action on the muscles. 
424. It is another interesting point of analogy between the 
action of Muscles and that of Electrical organs, that the former, 
like the latter, is attended with a change of electric state. In 
any fresh vigorous muscle, there is a continual current from the 
interior to exterior, which appears to depend upon the fact 
that the actions connected with the nutrition and disintegra¬ 
tion of its tissue go on more energetically in the interior of 
the muscle, than they do near its surface, where the proper 
muscular fibres are mingled with a large proportion of areolar 
and tendinous substance. During the contraction of a muscle, 
this current is diminished in intensity, or is even entirely 
suspended; but it is renewed again, so soon as the muscle 
relaxes.—An electric current has been found to exist also in 
Nerves; and its conditions are in most respects similar to 
those of the muscular current. 
CHAPTER X. 
FUNCTIONS OF THE NERVOUS SYSTEM. 
425. We have now completed our consideration of the 
Functions of Organic or Vegetative Life; those changes, 
namely, in the Animal body, which are concerned in the 
maintenance of its own fabric; and which, although per¬ 
formed in a different mode, and having different objects to 
fulfil, are essentially the same in character with those which 
take place in Plants. The first and most striking difference of 
mode results, as we have seen, from the nature of the food of 
Animals, which requires that they should possess a cavity for 
its reception, and a chemical and mechanical apparatus for its 
digestion (or reduction to the fluid form), in order that it may 
be prepared for absorption into the vessels. In regard to the 
absorption of the aliment, and its circulation through the 
system, there is but little essential difference between Plants 
and the lower Animals ; but in the higher tribes of the latter, 
we find that a muscular organ having the action of a forcing- 
pump is appended to the system of tubes in which the fluid 
