NERVE-CORD ACTION. 121 



.as little batteries from which the vis nervosa a mere 

 dead force like all other forces, and possibly electricity 

 is evolved. This view harmonizes with the facts which 

 indicate living action in them and distinguish them 

 from mere telegraph wires. Among these may be 

 noted, excitement by stimuli, such as pinching, prick- 

 ing, and other mechanical and chemical irritants in 

 any part of their course when entire, and even in the 

 peripheral ends when cut ; the cumulative action of 

 the vis nervosa shown by the greater effect of stimula- 

 tion of a nerve at a distance from its muscle than near 

 (Pfliiger) ; the increase of velocity of nerve current as 

 you approach the muscle (Munk); and a variety of 

 other facts, showing that "nerve excitement is not 

 simple conduction " (Eanke) ; for if the impression 

 conducted were merely the propagation of an impulse, 

 like waves it would grow weaker the farther from the 

 point of excitement owing to resistances.* The in- 

 fluence of the electric current in exalting and lowering 

 ;the irritability of the nerves is also, on the whole, 

 probably in harmony with this view of the constitu- 

 tion of the nerve cord, for a weak galvanic current 

 increases the irritability to other stimuli, while a 

 strong current weakens and ultimately destroys it, just 

 as we find with all other stimuli to vital action, and in 

 fact, irritability is always used by Fletcher as synony- 

 mous with vitalit}^. It is also in harmony with the 



* The explanation of Pfliiger is that the molecules of the nerve in 

 succession disengage active energy, and each stimulates its successor, 

 but the increase of action ("avalanche-like") shows that each molecule 

 disengages more force than the one before. Scale's is evidently a much 

 more natural explanation, for in it each little battery of protoplasm is 

 set in action by the passing current, and contributes its quota to the 

 current which is thus really swelled like an avalanche. 



