134 Shiro Tashiro 



sible. This failure, however, as he himself expected, was due to the 

 lack of delicacy of the chemical methods for detecting C0 2 . I ob- 

 served, with my apparatus that even a single kernel of a dry seed 

 gives off a definite quantity of CO 2 as long as it is alive. In ordinary 

 condition not only a living dry seed gives off more CO 2 than the dead 

 one, but also like the nerve, it always gives off more CO 2 when stimu- 

 lated by mechanical injury. In the normal condition, therefore, we 

 may safely conclude, there is always metabolic activity as long as 

 the seed is irritable, and that in the different states of irritability, 

 the respiratory activity is proportionately different. At present, 

 therefore, we have no decided evidence which will prevent us from 

 considering excitability as a function of respiration under ordinary 

 conditions. This relation is more directly studied by the use of 

 anaesthetics. 



I have already demonstrated that an etherized nerve gives off 

 considerably less CO 2 than the normal. Such an etherized nerve will 

 not give more CO 2 when it is crushed. This may be interpreted 

 by some to mean that the etherized nerve may be already dead. 

 This, however, is not the case. This objection, also, I have considered 

 by studying the nerve treated with KC1. 



When the nerve is treated with .2 m KC1 and then crushed, it does 

 not give an increase of CO 2 production. Mathews has shown that 

 while a .2 m. KC1 solution renders the nerve unexcitable, yet it will 

 recover its excitability by being replaced into n/8NaCl. These two 

 facts, therefore, support the idea that any agents that suppress excita- 

 bility of the nerves also decrease the C0 2 production and that C0 2 

 production by crushing the nerve must be largely due to stimulation. 

 This hypothesis is strikingly supported by similar observations on 

 the dry seed. Etherized seeds give much less CO 2 and cannot be 

 stimulated to give more C0 2 by crushing, while under normal con- 

 ditions, crushing a seed always increases its CO 2 production. Quan- 

 titative experiments in this direction will be given in another paper. 



These facts directly support Mathews' hypothesis that substances 

 which suppress irritability must act on the tissue respiration pri- 

 marily. If such an hypothesis is correct, we can easily picture what is 

 happening in the nerve fibre. Vernon 53 considers that a tissue 

 contains certain substances which can absorb oxygen from their sur- 



53 VERNON: Journal of physiology, 1909-10, xxxix, p. 182. 



