104 POLABIZED CONDITION OF THE CHAP. Et- 



stituting the muscular fibre being in a state of self- 

 repulsion whilst in this polarized condition, ■would 

 resist the force of molecular attraction unless depo- 

 larized; and, according to this view, the results of 

 muscular contraction would necessarily follow in 

 conformity to the law as laid down by Schwann. 



The nerve fibre existing also in a state of tension, 

 whatever influences this state would also produce a 

 depolarization of its fibre, the result being manifested 

 by muscular contraction, or pain. As it is only 

 during the period of this depolarization, when the 

 tension is altered, that contraction occurs, we have 

 some clue, as pointed out by Db. Todd*, to the 

 reason why contraction only ensues at the opening or 

 closing of the circuit, and not during the continuance 

 of the passage of the current along the nerve. The 

 constant current does not induce those momentary 

 changes necessary for the production of muscular 

 contraction ; it is only at the opening and closing of 

 the circuit that the tension of the fibre is affected. 

 The question, however, may be asked. How de we 

 account for the fact, that an inverse current through a 

 nerve will cause tetanic contractions, whereas a direct 

 current has no such effect? In this instance, tHe 

 inverse current may produce an altered condition of 

 the polarized state ; but I do not believe, as has been 

 already stated, that it increases the normal polarized 

 condition ; and if contraction be due to momentary 



•i Cyolopsedia of Anatomy and Physiology ; Art. " Physiology 

 of the Nervous System." 



