A CHEMICAL SIGN OF LIFE 



criticism, since there are many other evidences that the 

 metabolism of the nervous system is more intense than 

 that of any other tissue of the body. There is, as far 

 as we know, no physiological reason for assuming a 

 priori that the nerve has a lower metabolism than other 

 tissues, but, on the contrary, the direct and indirect 



TABLE III 



* All the figures are quoted from Schafer's Text Book of Physiology, I, 702, 707, and 

 708, except that of the isolated muscle, which I calculated from Fletcher (op. cit.). 

 Fletcher fails to state the weight of a leg, but gives the value o . 2 c.c. for one-half hour. 

 Hill believes that if we take each leg as 6 g. in average, the value will not be far from the 

 truth. 



f Fletcher fails to state the species of the frog, but it is inferred from Hill's paper. 



evidence shows that it has a more intense metabolism. 

 It is no doubt true, however, that an isolated nerve, such 

 as we have used, respires somewhat faster than the 

 same nerve intact in the body, because the effect of 

 cutting the nerve is to act as a stimulant. But, even 

 allowing for this effect, the metabolism still remains 

 markedly higher than that of most other tissues. We 

 may add here, however, that the hourly rate of output 

 of carbon dioxide from the resting nerve of a frog is 



