56 ANIMAL ELECTRICITY. LECTURE III. 



unfailing experiment. I had previously noticed that if 

 a frog is killed and its two sciatic nerves used in suc- 

 cession, the second nerve always gave larger varia- 

 tions than the first. I had also noticed that in the 

 case of a nerve that had been left lying for twelve 

 hours in the killed animal, the variation was extra- 

 ordinarily large — four or five times its usual value. 

 But I had never tried the effect of carbonic acid 

 upon such a variation. 



Fig. 19 (672). — Effect of C02upon a "carbonised " nerve, i.e., a nerve left for 

 24 hours subject to the reducing action of the surrounding muscles. 



Wanting to make the demonstration as clear as 

 possible with a good variation to start with, I took a 

 nerve that had been left for twelve hours in the frog 

 and got the result recorded on plate 672 (fig. 19), 

 to my considerable disgust. The stimulant action of 

 carbon dioxide was conspicuously poor, and I don't 

 think my friend watched the experiment out, in fact, 



