Acid Development in Nervous Tissue. 



19 



injured parts are pink, but crushed areas and the cut ends are 

 yellow. Microscopic examination showed the yellow color to be 

 located in the fibers near the point of injury. If a nerve be crushed 

 at a point previously uninjured, the development of acidity is 

 shown at once by the change in color from pink to yellow. Stimu- 

 lation of the nerve for five minutes with induction shocks causes 

 the acid reaction to develop between the electrodes. Previous 

 treatment with chloroform does not interfere with the reaction, 

 but heating to 50 0 C. in physiological salt solution inhibits it. 

 Killing the nerve with chloroform or by high temperatures does 

 not cause the development of acid. 



Assuming that the acid in question is either lactic or carbonic, 

 it is possible to show that it is the latter. For this purpose, a 

 method similar to that described by Haas 1 was used. Each tube 

 contained 3 c.c. Ringer's solution, to which were added three 

 drops of a 0.01 per cent, solution of the indicator. Carbon 

 dioxide was completely driven out by aerating with carbon- 

 dioxide-free air. The value of PH = 8.0. The tissue to be 

 tested was put into the tube, the latter closed by clamping the 

 short piece of rubber tube covering the end. The preparation was 

 inverted for an instant, righted, placed in the colorimeter and a 

 reading immediately taken. This reading is designated "start." 

 Each subsequent reading was made in the same way. When a 

 considerable amount of acid had been formed the tissue was 

 removed and the solution aerated for thirty minutes with carbon- 

 dioxide-free air. At the end of this time, in the case of nervous 

 tissue, the H ion concentration had returned to the initial value, 

 viz. : PH = 8.0. A piece of muscle run as a control gave off 

 both lactic and carbonic acid, as shown by the fact that it was 

 impossible to reduce the PH value to 8.0. These points are shown 

 in the table, giving a set of measurements from the tissues of the 

 same animal. 



TABLE. 



Brain, 72 Mg. 



Sciatic Nerve, 87 Mg. 



Blank PH =8.0 



Start PH =7.8 



10 min PH = 7.35 



Aerated PH =8.0 



Sartorius Muscle, 63 Mg. 



Blank PH =8.0 



Start PH =7.8 



10 min PH = 7.15 



Aerated. . . .PH = 7.6 



Blank 

 Start. 



PH = 8.0 



PH = 78 



PH = 6.8 



PH = 8.0 



10 min 



Aerated 



1 Haas, A. R., Science, N. S., Vol. 44, pp. 105-108, 1916. 



