747 



ill dilute solutions and tlieir influence increases according as tlieir 

 ions are more hydrophilous. The salts of a definite metal (Na) ha\e 

 been arranged in the order of the intensities of their inhibitory 

 influence upon the swelling. This series then shows the ions in 

 the order of their hydrophilous nature. The salts will impede the 

 action of the pepsin in the same order. In order to ascertain this, 

 I have made researches on seven salts of sodium, viz. citrate, acetate, 

 chloride, chlorate, nitrate, rhodanate and sulfate. A difficulty arose 

 in these experiments, viz. special caution was to be exercised to 

 prevent the salt from materially altering the Ch, as a change of 

 the Cn brings about a change of the charge of the protein and 

 consequently of the swelling. 1 fairly got over this difficulty by 

 taking the weak lactic acid. The measurements demonstrated that 

 the addition of salt caused only a slight change of the Cn. In 

 lactic acid solutions, with an acidity in the neighbourhood of the 

 optimum, the Ch can be allowed to fluctuate considerably before 

 any change in the digestion is noticeable. The changes noted by 

 me must, therefore, be ascribed to the action of the salt-ions. 

 Table IV shows the results of the experiments, in which the salt- 

 concentration was smallest ; this enabled us to estimate the results 

 more correctly than with more considerable salt-concentrations, 

 which atfect the swelling to such an extent as to render it almost 

 too small for a correct determination. 



TABLE IV. Experiments on the influence of salts. The salt-concentration is in- 

 variably 0.0067 equivalent. Temperature 15°; concentration of the 

 lactic acid 0.18 n. 



