744 



the ratio of the combined ions H/Cl being somewhat smaller for 

 pepsin than for albumoses. 



. The researches on the ion-combinations iiave yielded varions other 

 results : inter alia I found a more accurate value for the solubility 

 of mercuric chlorid than the one universally received. 



Furthermore the determinations of the Cl-ion-comhi nations with 

 albumoses have clearly illustrated the dissociation of the protein 

 chlorids, but I cannot discuss this point any further here. 



Second Set. Experiments on tke conditions under inhich the action 

 of pepsin takes place. 



From what lias been said thus far it is evident that Michaklis' 

 views as to the action of pepsin are not all correct. I have, there- 

 fore, tried to use another method in my researches on this action. 

 For the present the study of the condition of the enzyme offered no 

 prospect, as all we know about it is, that it is charged negatively 

 and probably combined with anions. On the other hand more success 

 might attend an attempt to observe the substratum; all the more so 

 because it had been given very little attention to as yet. 



The condition of proteins in solution with regard to the reaction 

 and the presence of salts, has been extensively studied in recent years. 

 We know that proteins are capable of combining with acids and 

 bases; that the compounds, which are in some way similar to salts, 

 can dissociate like the latter, but also that at a more considerable 

 concentration of the acids or the bases, this dissociation is arrested. 

 Furthermore it is highly probable that the protein-ions, liberated at 

 the dissociation, hydrate and swell. The more powerful the electric 

 charge of the protein, the more intense the swelling will be. With 

 continual addition of acid to a protein solution the swelling is made 

 to pass through a maximum ; the lessening of the swelling beyond 

 the maximum may be partly due to the reduced dissociation, but at 

 the same time to other causes also. 



We also know that salts affect the condition of proteins and that 

 they are capable of exerting influence in various ways. In small 

 concentrations and in acid or alkaline solutions the inhibitory action 

 of salts with regard to the electric charge and the swelling plays 

 the principal part. Various salts act in a different manner according 

 to the ions they throw into solution ; definite ions, especially the 

 sulfate-ion, are very powerful in arresting the swelling. 



In observing the action of pepsin we, therefore, had to take into 

 account the condition of the protein. In my first set of experiments 

 I could readily do this by employing Grützner's method to deter- 



