128 Shiro Tashiro 



non-medullated nerve should be reduced more from the figures found 

 for. the isolated nerve, than that of the medullated one. In other 

 words, by lowering 6.7 X io~ 7 gram which is the value for resting, non- 

 medullated, isolated nerves, the rate of increase of CO 2 by stimula- 

 tion in the uninjured nerve would become higher than 2.4 times, and 

 probably higher than 2.6 times, which is the rate for the medullated 

 nerve. This greater effect in the non-medullated nerve is what we 

 should expect if our present conception that conduction is in the 

 axis cylinder only, is correct. Before any accurate comparison of 

 the increase of CO 2 production on stimulation of non-medullated and 

 medullated nerves can be made it will be necessary, however, to 

 determine how much of the CO 2 from the resting nerve is due to injury 

 alone. Before we consider this point seriously, also, we should deter- 

 mine the metabolic activities of greater numbers of nerves of different 

 animals. Such an investigation is at present useless until we deter- 

 mine more quantitatively the relation between CO 2 production and 

 the various strengths of stimulation and the degree of excitability. 

 'If any uniformity of C0 2 output in respect to anatomical varia- 

 tions is discovered, light may be thrown on the function of the 

 medullary sheath and other differentiations. 



However insignificant these results may be as far as the similar 

 rates of the gas production of these two nerves is concerned, it should 

 be strongly emphasized that technical error plays no part in these 

 determinations. Inasmuch, as we are dealing with such an extremely 

 small amount of the gas, it is quite natural for those who are not 

 familiar with my apparati to suspect, by a hasty inspection of my 

 results, that the small differences I found under different metabolic 

 conditions may be due to mere experimental variations. For this 

 reason, particular attention is called to a detailed description of the 

 quantitative method I used, especially the footnote on page 144, 

 where I have cited a series of determinations of unknown quantities 

 of CO 2 in testing my apparati. I may repeat here that my experi- 

 ments with the spider crab and the winter skate were done at Woods 

 Hole 37 during the summer of 1911, while those with the frog were 

 done in Chicago during the winter of 1912. Under these different 

 conditions, I have not only used the different sizes of nerves, but also 



37 I take great pleasure in acknowledging my indebtedness for the kind accom- 

 modation offered me by Drs. Lillie and Drew at Woods Hole. 



