Carbon Dioxide From Nerve Fibres 119 



for the determination of the rate of oxidation, that a spot of cerebral 

 surface, if stimulated, loses its blue color owing to the using up of the 

 oxygen. 25 In case of the nerve fibre, however, we have already seen 

 that no direct evidence has ever been presented to show any chemical 

 changes connected with its activity, although there has been some 

 indirect evidence. As considered before, the failure of the direct 

 detection of CO 2 from the stimulated nerve must be due to the lack 

 of a delicate method. Thus using the new method we have already 

 demonstrated that a resting nerve gives off C0 2 , and will now attempt 

 to prove that nerves give off more C0 2 when stimulated. 26 



Electrical Stimulation of non-Medullated Nerve. Owing to the 

 scope of delicacy of the new method, which is sensitive to as small a 

 quantity as i.o X io~ 7 gram (an amount corresponding to the CO 2 

 contained in -^ cc. of pure air), the utmost caution must be taken to 

 prevent any complication which may result in formation or absorption 

 of minute quantities of C0 2 . After I had found by experiment that 

 there is no appreciable increase of CO 2 due to the direct electrical 

 decomposition in the nerve when stimulated by a weak induction 

 current and that several other forms of stimulation qualitatively 

 confirmed the results obtained by the electrical stimulation, I have 

 naturally employed the induction current as a stimulant in all my 

 experiments on the quantitative estimation of CO 2 production from 

 the stimulated nerve. 27 



As Table V shows, the stimulated non-medullated nerve fibre of 

 the spider crab gives off 16. X io~ 7 grams of CO 2 for 10 milligrams of 



25 HILL: loc. cit. 



26 Professor Carlson has very kindly called my attention to a recent publica- 

 tion from the Physiologisch Laboratorium der Utrechtsche Hoogeschool, in which 

 Buijtendijk reports that certain head nerves of fishes take up more O 2 when 

 electrically stimulated. He could not, however, find any increase of O 2 con- 

 sumption in the sciatic of the frog. Also see: Koninklijk Akademie van 

 Wetenschappen, Amsterdam, afd, xix, pp. 615-621. 



Haberlandt also recently reports (Archiv fur Physiologic, 1911, p. 419) that 

 the resting nerve takes up of O 2 , 41.7 - 33-4 cmm. at 19 - 24 per gram per 

 hour. When this nerve is excited, intake of O 2 is increased. Since the respira- 

 tory quotient of the stimulated nerve is equal to that of the resting, he con- 

 cludes that when the nerve is excited, it must give off more CO 2 . He does 

 not, however, indicate how much CO 2 is produced by stimulation. 



27 Use of non-polarizable electrodes was impossible for my apparatus, for the 

 presence of foreign liquid in the chamber interferes with C0 2 estimation. As 



