166 Prof. A. B. Macallum and Miss M. L. Menten. [July 24, 



The results of investigations on the electrical properties of nerve fibres,, 

 however, show that the relationship between the electrolytic action of 

 a current on the nerve and its exciting efficiency is a very intimate,, 

 practically an indissoluble, one, and in view of this one asks on what 

 constituent the electrolytic effect is exerted.* 



The observations of one of us show that in the axons of the normal nerve 

 fibre potassiumf in any of its combinations is wholly wanting, and, therefore, 

 the electrolytes present must be those of sodium, calcium, and magnesium 1 

 compounds, but as the two latter elements are present only in very minute 

 quantities each as compared with sodium in nerve tissue, and as, further,, 

 the inorganic phosphates are not found when sought for micro-chemically 

 in the axon, the indications point very distinctly to the occurrence there of 

 chloride, of sodium. 



The difficulty in demonstrating the occurrence of chlorides in tissues 

 hitherto has been that the one sensitive reaction for chlorides, i.e., the 

 formation of argentic chloride and the reduction of this to subchloride under 

 the action of sunlight, was not distinguishable from that involving com- 

 pounds of silver formed with proteids and organic compounds generally,, 

 which also were supposed to reduce under the action of sunlight. When, 

 therefore, a solution of a silver salt gave a coloured reduction compound on 

 its application to a tissue in sunlight, it was held not to be determinable 

 .what was due to chlorides and what to organic compounds. 



This difficulty, the senior author has shown,t can be overcome if in the- 

 reagent itself there is present a quantity of free nitric acid which prevents 

 the formation from phosphates, sulphates, and carbonates, and from all 

 organic compounds of tissues, except creatin and taurin, of coloured reduction 

 combinations of silver, and he found, further, that when albumins, globulins,, 

 and gelatins are freed from all traces of chlorides, they do not manifest the 

 slightest capacity to form with silver salts compounds which " reduce 

 under the action of light. 



It became evident, therefore, that a solution of nitrate of silver, containing 

 a quantity of free nitric acid, could be used to determine the occurrence and 

 distribution of chlorides in nerve fibres, and, in consequence, the authors 

 began the observations of which this paper is the outcome. 



* A very interesting discussion of this subject is given in J. S. Macdonald's paper on 

 " The Injury Current of Nerve : ^The Key to its Physical Structure," ' The Thompson 

 Yates Laboratories Eeport,' vol. 4, 1902, p. 213. 



t Macallum, "On the Distribution of Potassium in Animal and Vegetable Cells,"" 

 'Journal of Physiol.,' vol. 32, p. 95, 1905. 



X Macallum, " On the Nature of the Silver Eeaction in Animal and Vegetable Tissues," 

 ' Roy. Soc. Proc.,' vol. B 76, p. 276, 1905. 



