50 DYNAMICS OF NERVE CELLS. II 



Method. 



The rate of formation of even the small amount of carbon dioxide 

 evolved from ganglia, each weighing only 12 to 30 mg., is not difficult 

 if one uses the indicator method of Sorensen^ as modified for tissue 

 work by Osterhout and his collaborators.^ The method of Tashiro/ 

 who demonstrated that the Limulus ganglion produces CO2, did not 

 admit of rapid variation of the temperature and was not adaptable to 

 our purpose. 



The indicator method was used with the technique and precau- 

 tions described by Moore. ^ The velocity of the reaction at different 

 temperatures is determined by finding the time required to change the 

 hydrogen ion concentration of an immersion fluid from pH 7.7 to 



7.4 using phenolsulfonephthalein as the indicator.^ 



Buffer must be avoided in the immersion fluid which was a balanced 

 saline solution of the following composition: 100 parts of m/2 NaCl, 



1 .5 parts of m/2 KCl, and 2.2 parts of m/2 CaClg, to 1 liter of which 

 15 cc. of 0.01 per cent phenolsulfonephthalein were added. The de- 

 sired initial alkaUnity (pH 7.7) was obtained by adding the requisite 

 amount of NaOH. 



The color comparisons were made in "Pyrex" glass tintometer 

 tubes of about 4 cc. capacity, all of the same diameter, and filled with 

 solution to a 3 cc. graduation mark. The tubes were stoppered with 

 corks impregnated before each experiment with neutral, boiling paraf- 

 fin or with rubber stoppers boiled in distilled water, paraffin-coated, 

 and assuredly free from acid. The tubes and fluid were brought to 

 the desired temperature before the ganglion was introduced and then 

 kept at a constant temperature in large vessels of water. At the low 

 temperatures it sometimes became necessary to adjust the tempera- 



2 Sorensen, S. P. L., Biochem. Z., 1909, xxi, U\;Ergehn. Physiol, 1912, xii, 393. 



3 Osterhout, W. J. V., /. Gen. Physiol, 1918-19, i, 17, 171. Gustafson, F. G., 

 /. Gen. Physiol, 1918-19, i, 181. Brooks, M. M., J. Gen. Physiol, 1918-19, i, 

 193. Thomas, H. S., /. Gen. Physiol, 1918-19, i, 203. Irwin, M., /. Gen. 

 Physiol, 1918-19, i, 209. 



•* Tashiro, S., A chemical sign of Hfe, Chicago, 1917. 

 ^ Moore, A. R., /. Gen. Physiol, 1918-19, i, 613. 



* The author is indebted to Prof. A. R. Moore who cooperated in the initial 

 experiments of this investigation. 



