Carbon Dioxide From Nerve Fibres 131 



that the respiratory quotient of the resting and acting nerve is nearly 

 unity. Since he found that O 2 consumption is increased when stimu- 

 lated, and since the respiration quotient remains constant before and 

 after the stimulation, he concluded that it must give off more CO 2 

 when stimulated. It is very interesting to compare the O 2 consump- 

 tion in this experment with the CO 2 production of mine. 46 



Taking his lowest figure, because he worked in 19 - 24 and I in 

 19 - 20, 41.7 cmm. of O 2 amount to .00007 cc - f r j o milligrams for 

 ten minutes. My figure of 5.5 X io~ 7 grams for the same units may be 

 translated to .00027 cc. of C0 2 (ignoring temperature and pressure 



C0 2 00027 



correction). Therefore- = - - = 3. 8, the respiratory quotient. 



O 2 00007 



As I have not determined O 2 consumption of the nerve of Rana pipiens, 

 this figure has no particular value, but the fact that the CO 2 produc- 

 tion is comparatively higher than 2 consumption is a matter of 

 considerable interest. 



One of the most important observations made by A. V. Hill 47 

 is the fact that he could not detect any rise of temperature in a frog's 

 nerve as measured by an apparatus which is sensitive to a change of 

 one-millionth of a degree. From this, according to his calculation, 

 he concludes that not more than one single oxygen molecule in every 

 cube of nerve of dimension of 3.7 //, can be used up by a single propa- 

 gated nerve impulse. Therefore, he suggested that an impulse is 

 not of irreversible chemical nature but a purely physical change. 



Although, I confess, my ignorance makes it impossible to interpret 

 his valuable results from my observations, I may add that these two 

 apparently irreconcilable facts may throw light on the true nature of 

 nervous metabolism. Dr. Mathews has suggested that metabolism 

 in the nerve may be something of the order of alcoholic fermentation, 

 which is not a direct oxidation, and where heat production cannot 

 be so large as CO 2 production, since the energy content of glucose is 

 only a trifle higher than that of the alcohol produced. The compara- 

 tively little heat production in the case of working glands is a matter 

 of interest in this connection. At any rate we should not forget the 



46 He used Rana esculenta, which, by the way, gives for the whole animal 

 .082 g. CO 2 per kg. per hour at 17 according to Schultz. My frog was Rana 

 pipiens. 



47 'HILL: Journal of physiology, 1912, xliii, p. 433- 



