594 



PHYSIOLOGY. 



produces death of the superficial layer of a segment next the cut sur- 

 face. The dead tissue behaves negatively with regard to the living, 

 and the electromotor forces accordingly have their seat at the plane 

 of demarcation between the dead and living. As to the action cur- 

 rents, they are explained by admitting that during stimulation 

 the active parts are negative with regard to the parts at rest. 



Waller has compared the action of ether and chloroform on the 

 electrical currents of a nerve. The movements of the galvanometer 

 mirror are photographed. He has shown that chloroform is more 

 toxic than ether by this method. 



The nerve had in each case a maximum dose; that is, for a 

 period of one minute, air saturated with the drug, that is about 



Be. ore. 



Alter. 



Fig. 230. Effect of Chloroform upon the Electrical Responses of 

 Isolated Nerve. (WALLER.) 



The electrical response is definitely abolished; there is no recovery during 

 the period of observation. With ether it gradually recovered. 



50 per cent, of ether and about 12 per cent, of chloroform. In the 

 case of ether, the effect was quite typical, an abolition of excitability 

 in about three minutes. In the case of chloroform, the excitability 

 was promptly abolished, and on testing the nerve a half hour after- 

 wards the nerve has definitely lost its excitability; that is, dead by 

 chloroform. 



Theories of Muscle and Nerve Electrical Currents. There are 

 two theories, one of Du Bois-Reymond, the molecular, the other that of 

 Hermann, that of alteration. 



MOLECULAR THEORY. The molecules may be considered to bo 

 positive on their longitudinal surface, and negative on their trans- 

 verse section. Their negative surface is turned towards the onds 

 of the muscle or nerve, and the positive surfaces directed toward- 



