616 



RESPIRATORY RATE OF SCIATIC NERVE OF FROG 



by the recovery of the tint corresponding to the initial pH value of 

 the solution. By the use of Hopkins' thiophene test I have found 

 that brain tissue produces small amounts of lactic acid as the result 

 of cooking. But any lactic acid produced by injury to nervous 

 tissue in my experiments presumably reacted with the carbonates 

 of the tissue causing carbon dioxide to be given ofi. 



It is apparent that the first problem in determining tissue respira- 

 tion is to eliminate the acid of injury from the measurements. This 

 proved to be a simpler matter than at first seemed possible, because 

 it was found that the acid is given off only during a very short period 

 after injury. This can be shown by determining the rate of acid 



TABLE I. 



Effect of Crushing on Rate of Acid Production. 



Sciatic nerve. 



*Rate 



100 



seconds 



. Temperature 18-19°C. 



output of a sciatic nerve, before and after crushing. The rate in- 

 creases at once as a result of the acid produced by the injury but 

 falls rapidly to the original rate. This indicates the" momentary 

 character of the production of the acid of injury and proves its rapid 

 elimination.^" Table I illustrates this point. 



It is therefore possible by making a number of successive readings 

 for each point, and by discarding the first readings, to obtain a fairly 

 accurate estimation of the respiratory rate of the tissue by this 

 method. In case the periods of time were not long, i.e. less than 3 

 minutes, five successive readings were taken, and an average of the 



10 Moore, A. R., Proc. Soc. Exp. Biol, and Med., 1918-19, xvi, 35. 



