EXCITATION AND CONDUCTION 61 





 We have already mentioned the effect of ether on 



nerves and demonstrated that lowering the excitability of 

 a nerve is accompanied by a lowering of carbon dioxide 

 production. For the quantitative experiments, carried 

 out in conjunction with Dr. Adams, we used chloral 

 hydrate and ethyl urethane in preference to the ordinary 

 volatile narcotics. If we anesthetize a nerve with the 

 lowest concentration of ether or chloroform that pro- 

 duces a reversible loss of irritability, then the anesthe- 

 tized nerve regains its excitability during the course of the 

 experiments, for in order to make the apparatus free 

 from carbon dioxide after introducing the nerve we have 

 to wash it with carbon-dioxide-free air several times. 

 By so doing the most volatile narcotics are removed 

 from the nerve. On the other hand, if we use higher 

 concentrations, which, as we know, lower carbon dioxide 

 production, we may be subject to the criticism that the 

 lowering of metabolism may be due partly to death or 

 injury. It is therefore essential that we should investi- 

 gate the effect of various concentrations, from such as 

 have apparently no narcotic effect to those from which 

 recovery is doubtful or absent. Thus the use of suitable 

 narcotics as well as concentrations seems to be of prime 

 importance. For even those who consider that narcosis 

 is not due to an asphyxiation admit that the oxygen 

 consumption is greatly depressed if the narcosis is pushed 

 too far, although such depression in the rate of oxidation 

 may have nothing to do with the cause of the narcosis. 



With a view to studying the effect of various con- 

 centrations of anesthetics, the claw nerve of a crab was 

 isolated, its excitability tested by electrical stimulation, 

 and, without being cut off from the claw, it was immersed 



