iv ELECTROMOTIVE ACTION IN MUSCLE 351 



series of molecules constantly passes over into the adjacent series 

 by a loop-like circuit, and thus presents no free cross-section." 

 If a single such " molecule," or better, aggregate of molecules, lay 

 singly embedded in a conducting fluid, it would evidently react 

 in every particular like a peripolar molecule of du Bois ; collect- 

 ively, however, these cannot, like the latter, be conceived as sur- 

 rounded by molecular currents, since the potential on all sides 

 seems to be neutralised. The same objections as obtain against 

 the original molecular theory also to a great extent apply to its 

 " electro - chemical " translation, while the excessively detailed 

 presumptions of the latter re chemical structure of living sub- 

 stance must a priori give rise to much reflection. 



According to Grlinhagen's theory, we must assume an electro- 

 motive opposition between each primitive fibril and the surround- 

 ing nutritive fluid (sarcoplasma), whereby the latter represents 

 the positive, the fibrils the negative, link of the chain. The 

 absence of current in uninjured muscles would, on this theory, 

 be very simply explained by the immersion of the negative 

 electrical fibrils in the positive nutritive fluid. Griinhagen's 

 views of the cause of electromotive action in animal tissues 

 originated in experiments with porous cylinders. Yet, as Her- 

 mann points out, it is difficult to see how these experiments 

 apply to the given relations in muscle. Griinhagen found, 

 namely, that cylindrical, porous bodies, during the moistening of 

 their cross-sections (end-surfaces), exhibited difference of electrical 

 potential towards points in the middle of their longitudinal sur- 

 face, and also between asymmetrical points of the two surfaces 

 in themselves in the same direction as the muscle cylinder. 

 These differences of potential disappear when the porous cylinder 

 is saturated with fluid, and is therefore to be viewed as an effect 

 of the passage of fluids through the porous substance. Griinhagen 

 imagines the relation between fibrils and surrounding nutritive 

 fluids to be similar. 



The third theory relative to the seat of electromotive action 

 is the alteration-theory of L. Hermann^ which is in perfect agree- 

 ment with all the facts known to us. This theory refers all electro- 

 motive activities of living tissue to chemical changes of the 

 substance without regard to its molecular structure. With 

 reference to the "resting" muscle current, the theory proceeds from 

 the postulate, "that dying substance is negative to living substance." 



