no Shiro Tashiro 



itself, but may, also, aid in forming a fundamental conception of the 

 tissue respiratory mechanism. In this way, if the protoplasmic irri- 

 tability has a direct connection with the cellular respiration, then 

 our idea of the general nature of the pharmodynamics of many 

 reagents on a living tissue may be essentially modified. 



METHODS AND MATERIALS 



Two new apparati were constructed which will detect CO 2 in as 

 small quantities as one ten-millionth of a gram and estimate it with 

 quantitative accuracy. The detailed method has been described in 

 a separate article. 12 



Preliminary experiments with these new apparati showed that the 

 sciatic nerves of dogs gave too large quantities of CO 2 for my method 

 so that I was compelled to use a smaller nerve of a cold-blooded 

 animal for quantitative estimation. For exact measurements of CO 2 

 production, I have used only two kinds of nerve, although I have used 

 a large variety of nerves in qualitative experiments. For a non- 

 medullated nerve fibre, Prof. G. H. Parker 1S was so kind as to sug- 

 gest to me that I use the nerve trunk of the claws of the spider crab 

 (Labinia Caniliculata) which is a bundle of mixed sensory and motor 

 fibres. The frog, whose sciatic was used as a representative for 

 medullated nerve, was exclusively Rana pipiens, obtained from 

 Indiana. 



As my apparati in the present form cannot be used for a muscle 

 nerve preparation nor for the normal nerve in situ, the use of an 

 isolated nerve could not be avoided. Experimental factors thus intro- 

 duced should be carefully considered before we interpret the observa- 

 tion as a normal metabolism. This serious objection, however, can be 

 overlooked, as far as our fundamental question of different metabolic 

 activities before and after a stimulation is concerned, for Waller 14 

 has demonstrated that the presence of excitability in an isolated 

 nerve persists as long as nineteen hours provided that the electrical 

 changes correctly represent the state of excitability. Although 



12 See pp. 137-145- 



13 For this and other suggestions, I am under great obligation to Dr. Parker. 



14 WALLER: 1896, Brain, xix, p. 53. 



