490 PROCEEDINGS OF SECTION D. 



7.— ON SOME RECENT ADVANCES IN OUR KNOWLEDGE 

 OF THE SALTS OF PROTEINS AND OF THEIR 

 ROLE IN BIOLOGICAL PHENOMENA. 



By T.. BRAILSFORB ROBERTSON', B.Sc, Instructor in Fhysiology in the 

 University of California. 



It is a fact which has for some time been familiar to physical 

 chemists that the activities of many chemical reagents are functions of 

 their degree of dissociation or ionisation; thus the electric conductivity of 

 a solution of an acid, the depression of the freezing point of the solvent 

 which produced by it, its tendency to displace other acids from the 

 bases with which they are combined, and the acceleration of the hydro- 

 lysis of cane sugar or of methyl acetate which it can bring aboixt are all 

 intimately connected with the degree to which the acid is dissociated 

 into ions. 



The first clear indication of the importance of electrolytic dissocia- 

 tion in biological phenomena was afforded by the experiments of Dreser 

 (1), who, in 1893, showed that the greater the concentration of free 

 mercury ions in a solution of a salt of mercury the more toxic is the 

 solution for yeast cells; and, moreover, that the formation of complexions 

 containing mercury diminished the toxicity of the solution. Thus a 

 solution of potassium mercury thiosulphate contains but little mercury in 

 the form of mercury ions, for the mercury combines with two SOg groups 

 to form complex ions which no longer possess the characteristic proper- 

 ties of free mercury ions. Such a solution is but slightly toxic for yeast 

 cells, but a solution of another salt of mercury, such as the sulphocya- 

 nate, containing precisely the same percentage of mercury as the 

 solution of potassium mercury thiosulphate, is highly toxic, for in this 

 solution the mercury exists in the form of free mercury ions. 



These experiments of Dreser's were followed in 1895 by those of 

 Klem (2), who found the actions of different strong acids in disinte- 

 grating the protoplasm of cells were identical, and he attributed the 

 disintegration to the hydrogen ions of the acids. 



In 1896 the papers of Kahlenberg and True (3), and of Heald (4), 

 appeared, in which they described extensive experiments showing that 

 equivalent concentrations of strong acids, and also, in Heald's investi- 

 gations, equivalent concentrations of different salts of copper were 

 equally poisonous for plants. In 1 896, also. Paul and Kronig (5), showed 

 that, in general, the more highly ionised a salt is — such as salt of copper 

 or mercury — the more powerful is its toxicity for bacteria, and, therefore, 

 the more intense is its action as a disinfectant. 



In 1897 Loeb (6) showed that the amount of water taken up by 

 a frog's muscles, excised and immersed in solutions of strong inorganic 

 acids, was dependent upon the hydrogen ion of the acids, since equal 

 quantities of the hydrogen ion in a given volume of these acids produced 

 quantitively equal effects. In the same way the absorption of water by 

 muscles placed in solutions of strong inorganic bases could be referred to 

 the hydroxyl ion of the bases. 



