Carbon Dioxide From Nerve Fibres 125 



Unless it is proven that CO 2 production from the injured muscle is 

 quantitatively equivalent to lactic acid formed, their interpretation 

 cannot be applied to the injured nerve, for in the case of the " plateau " 

 of the survival muscle respiration, when in complete loss of irritability, 

 the lactic acid yield remains stationary, Hill calculated that the C0 2 

 production corresponds to the amount liberated from the carbonate 

 of the tissue by the lactic acid formed. 31 



Furthermore, if their interpretation is applied to the nerve, the 

 fact that etherized nerves or nerves rendered unexcitable by KC1 do 

 not increase CO 2 output when crushed, cannot be explained. The 

 fact that only excitable nerves when injured increase their CO 2 pro- 

 duction, is a sufficient proof that some sort of stimulation is applied 

 to the nerve when crushed, the tissue destruction, no doubt, following 

 afterward. The increase of CO 2 production on crushing the living 

 nerve and its absence on crushing the anaesthesized nerve is the point 

 that I want to emphasize here in order to confirm my results obtained 

 by electrical stimulation. I may add here that a perfectly parallel 

 increase of CO 2 by crushing has been observed hi dry seeds, including 

 wheat, wild oats, Lincoln oats, Swedish select oats, leaves of Japanese 

 ivy, and spinal cords of rabbit. 32 



Chemical Stimulation. The study of the nature of chemical 

 stimulation has been so thoroughly made 33 that at first it was thought 

 that chemical reagents would be ideal as stimuli. 



It was soon discovered, however, that the presence of minute 

 quantities of a foreign liquid is such a disturbing factor that stimula- 

 tion by salt solutions could not be used for quantitative experiments. 

 With a qualitative analysis, however, I found a variety of evidences 

 which show that the nerve* stimulated chemically gives off more CO 2 , 

 and that the nerve rendered less excitable by reagents decreases CO 2 

 production. 



When each sciatic nerve of a frog is isolated and one is left in the 

 normal saline in one case, and in the body of the frog in the other, for 

 the same length of time, and then transferred to the two chambers of 

 the apparatus, if the quantities of the precipitate are compared, it is 

 found that the nerve which has been in normal saline gives more CO 2 . 



31 HILL: Journal of physiology, 1912, xliv, p. 481. 



32 Fuller discussion of these will appear in a subsequent paper. 



33 MATHEWS: This Journal, 1904, xl, p. 4555 ^os, riv P- 20 3- 



