_ 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 
