Carbon Dioxide From Nerve Fibres 113 



enough CO 2 to give the precipitate in ten minutes. If it does, a fresh 

 nerve is prepared and a less volume of the gas is withdrawn; if it 

 does not, a larger volume should be taken till the precipitate appears 

 within ten minutes. (See footnote, page 140.) 



In this way, by repeated experiments with several fresh nerves, 

 a minimum volume of the gas for a known weight of the nerve which 

 gives a precipitate is determined. This minimum volume should 

 contain exactly a definite quantity of CO 2 namely i.o X io~ 7 

 gram. 22 



In this way, since we know the original volume of the respiratory 

 chamber from which this minimum volume is withdrawn, and since 

 we know the quantity of CO2 contained in this volume, it is easily 

 calculated, how much CO 2 is produced by the nerve during the known 

 period. It should be understood that in determining the minimum 

 volume of gas taken from the respiratory chamber, a series of experi- 

 ments were conducted in order to calculate both the minimum volume 

 which just gives the precipitate and the maximum volume which 

 does not give the the precipitate for a known weight of the nerve for 

 a known period of respiration In the tables following, columns 8 

 and 9 refer to these volumes calculated from experiments. 



Table I, gives the result for a non-medulla ted nerve. 



Medullated Nerve Fibre. For the quantitative estimation of 

 C0 2 production from the medullated nerve I have taken a frog's 

 sciatic, using apparatus 2. The results given in Table II, obtained by, 

 similiar methods, show that each ten milligrams of the frog's sciatic 

 nerve gives off 5.5 X icr 7 grams for the first ten minutes. 



A large quantity of nerves were tested and it was determined 

 whether or not all resting nerves give off CO 2 . As a result, I found 

 no exception in any of them. The following varieties of nerves 

 were examined: 



1. MOTOR NERVE: Occulo-motor nerve of the skate. (Raia Ocallata.} 



2. SENSORY NERVE: Olfactory nerve of the same. (Raia Ocallata.) 



3. MEDULLATED NERVE: Sciatic nerve of the dog, frog, turtle, mouse; 

 optic nerve of the skate. (Both Raia Ocallata and Raia Erinecia.) 



4. NON-MEDULLATED NERVES: Nerves of the spider crab; olfactory nerve 



of the skate. (Raia Ocallata.) 



5. NERVE OF INVERTEBRATE: Spider crab's nerves. 



22 See p. 140. 



