30 LAB OR A TOR Y G VIDE IN PH YSIOL OGY. 



ing a contraction of the muscle. Keep the key 

 closed. 



(9) Quickly rotate the limbs from minimum to maxi 

 mum; the muscle responds. Quickly rotate from 

 maximum to minimum; the muscle responds. 



From the preceding observations one may con- 

 clude that response to electrical stimulation is elic- 

 ited not by the simple flow of an electric current 

 through the irritable tissues, but by a more or less 

 sudden change in the strength of the current. The 

 opening and closing of a galvanic current, also its 

 sudden increase or decrease, serves as an efficient 

 stimulus, while the gradual increase or decrease in the 

 strength of the current causes no response. 



of( 



> .""'/, 



3 



