132 Shiro Tashiro 



anatomical as well as the chemical differences between muscle and 

 nerve. In this respect the ratio between CO 2 production and 2 

 consumption from the nerve is suggestive. 



The extremely small intake of O 2 has another point of interest in 

 relation to the general nature of irritability. It has been repeatedly 

 reported that a nerve can remain excitable several hours in an oxygen- 

 free atmosphere, although there is no doubt its excitability diminishes, 

 yet there is a considerable amount of evidence to show that oxygen 

 is very closely associated with the state of excitability, To har- 

 monize these two facts, the oxygen-storage hypothesis has been 

 suggested, by which the exhaustion is attributed to complete consump- 

 tion of "the stored oxygen and that excitability is restored when 

 atmospheric oxygen is readmitted. Without committing ourselves to 

 this hypothesis, I may add that according to Haberlandt's figure, the 

 resting nerve of 10 milligrams will consume only .0042 cc. O 2 in ten 

 hours. If we take our figure and assume that one volume of oxygen 

 was necessary to produce one volume of C0 2 (this assumption is made 

 without any significance except to give a liberal estimate), the C0 2 

 production would require about .015 cc. of O 2 for ten hours. And if 

 we assume again that activity will increase O 2 consumption in propor- 

 tion of C0 2 production, then it means that the nerve when stimulated 

 takes up only .03 cc. of O 2 during ten hours stimulation. I am not 

 aware, at present, of the existence of any method which will surely 

 remove O 2 as completely as this from a large vessel; and this is a 

 very liberal estimate. My experiences in rendering the air free from 

 CO 2 encourages me to raise the question, How can one remove every 

 trace of 2 from a nerve fibre? Without having a correct criterion 

 for an oxygen-free medium we cannot at present consider definitely 

 any question of the relation of O 2 to irritability. 



CONCLUSION 



In spite of all the negative evidence against the presence of meta- 

 bolism in the nerve fibre, we have established three important facts: 

 namely, (i) A resting nerve gives off a definite quantity of carbon 

 dioxide; (2) stimulation increases CO 2 production; and (3) CO 2 

 production from the resting nerve proportionally decreases as irri- 



