86 POLARIZED CONDITION OF THE CHAP. VIII. 



which the muscular or the nerve current may occur 

 will be of the utmost importance to bear in mind : 

 whether as the act of nutrition, or during nutrition ; 

 or whether as the result of nutrition, i. e. from the 

 polarized condition of the fibre itself, since they may 

 be referred to two distinct classes of actions. Their 

 primary dependence, however, upon nutrition is a 

 circumstance of some importance ; and it would 

 appear that this polarized condition of the tissue 

 is intimately connected with the so-caUed vital con- 

 dition of the parts ; the irritability of the muscular 

 fibre and the sensibility of the nervous tissue being 

 perhaps dependent upon it. 



As the constituents of a muscle or its particles 

 must be in a state of self-repulsion, the electrized 

 or polarized condition not being limited to the 

 surface, as in a metallic conductor, but the whole 

 substance of the muscle throughout being equally 

 and bodily polarized, the question arises. Might not 

 muscular contraction be the necessary result of the 

 attraction between the psirticles, the muscular sub- 

 stance being, as it were, depolarized by nervous agency ; 

 and the force by which the state of tension in the 

 muscle was maintained being evolved and set free 

 or made manifest in some other form or mode of 

 action, according to circumstances? In a future 

 chapter we shall see that some evidence has been 

 obtained, indicating that, during extraordinary mus- 

 cular exertion, some force is evolved, as in the fish ; 

 but during ordinary muscular exertion, the force may 



