5l8 COMPARATIVE ELECTRO-PHYSIOLOGY 



response of the tissue. A record of the various phases in 

 the effect of chloroform on the mechanical response of nerve 

 is found in fig. 319. It will be seen here that the first effect 

 of chloroform was to cause a great enhancement of ex- 

 citability, which in this case lasted for about a quarter of an 

 hour. I have given only two responses of this series. After 

 this, the responses began to decline, and another very 



FlG. 319. Photographic Record showing Effect of Chloroform on 

 Mechanical Response of Frog's Nerve 



First pair of responses, normal ; second pair, preliminary exaltation on 

 application of chloroform ; last series exhibit subsequent effect of 

 chloroform in unmasking the positive component as diphasic response. 

 Expansion is here followed by contraction. Note regular waning of 

 both components with growing anaesthetisation. 



interesting reaction made its appearance. The impinging 

 stimulus had hitherto induced only an immediate contractile 

 response. But by the action of the chloroform the excitatory 

 effect was delayed, and the positive, or mechanically ex- 

 pansive response was unmasked in the form of a preliminary 

 downward twitch. Response was now, therefore, diphasic 

 positive followed by negative. Immediately on the applica- 



