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 



