The carbon dioxide of injury and of respiration in nervous tissue

Abstract

It has been shown that injured nervous tissue gives an acid reaction with phenolsulphonephthalein as indicator and that the acid measured by Haas 1 method is carbon dioxide. 2 If the rate of acid output of a frog's sciatic nerve be measured by taking the time required for the solution to change tint from pH 7.8 to pH 7.4, this rate will be seen to fall after the first or second consecutive readings. If now the nerve be taken out and crushed with a glass rod, the subsequent measurement will show a large increase in rate, which, in turn, after a few readings, falls to the former low rate. The following determinations on a pair of frog sciatic nerves shows this fact.

It is apparent that the acid resulting from injury develops only momentarily and is soon washed out by the surrounding neutral Ringer's solution. It therefore seems reasonable to suppose that the carbon dioxide output during the time following is largely that of respiration.

With a view to comparing the rates of acid production of central nervous system, muscle and nerve fiber, equal weights of the medulla, the sartorius muscle, and the sciatic nerves of the same individual frog were taken. The Haas measurements were made by putting the tissue to be tested into a small test-tube containing 3 c.c. of Ringer's solution tinted with the indicator and previously rendered pH 7.8 with a drop or two of n/10 NaOH to the liter. The tube was closed with a paraffined cork. A bubble of air acted as a stirrer and the preparation was inverted and righted at short intervals until the tint of the solution matched that of a standard tube of solution whose pH = 7.4.