LOd PROCEEDINGS OF SECTION D. 



The fact that proteins can combine either with acids or with bases 

 indicates that they belong to that class of bodies known as amphoteric 

 electrolytes, or, in the briefer terminolo^jy which I have recently elsewhere 

 suggested, (68) ampholytes. Ampholytes are bodies which can split off 

 either hydrogen or hydroxyl ions when in solution. The amino-acids, 

 for example, are typical instances of this type of bodies. Tlie NH2 group 

 in amino-acetic acid probably combines with H.^O when dissolved in 

 water so that it splits off hydroxl, while the COOH group, in the usual 

 way, splits off hydrogen ions. The polypeptids of Emil Fischer (69) are 

 ampholytes simply formed by the NH2 group of one ampholyte com- 

 bining with the COOH group of another, so that the resultant molecule 

 still retains an uncombined NH2 group and an uncombined COOH group. 

 The amphoteric properties of proteins and the large number of amino- 

 acids obtained by their decomposition probably indicate a structure 

 similar to Fischer's polj'-peptids. The attempts which have been made 

 to apply to solutions containing proteins the ordinary laws of chemical 

 statics and dynamics, such as apply in solutions containing only dilute 

 non-amphoteric electrolytes, have met with varying success. The re- 

 searches of W. B. Hardy on globulin (70) and those of Bugarszky and 

 Liebermaum (71) on albumin and alnumose have been successful in 

 proving that these proteins combine with acids in molecular proportions, 

 and those of Laqueur and Sackur (72) and of Van Slyke and Hart (73), 

 and others, have shown that casein combines with bases and acids in. 

 equivalent-molecular proportions. The attempts to formulate a mass- 

 relationship between salts and proteins have, however, met with great 

 difficulties. Thus, Galeotti and Guerrini (74) find that when protein is 

 precipitated by salts the proportion of salt to protein in the precipitate 

 varies continuously. Not even in the case of salts of the heavy metals 

 is there any constant proportionality beween the concentration of the salt 

 and the amount of protein precipitated (75). Hardy, however, considers 

 that compounds between globulin and salts are formed, but that they are 

 stable only when their dissociation is completely suppressed by excess of 

 salt (70). Recent observers agree in .stating that the rate of hydrolysis 

 of proteins by pepsin, trypsin, and erepsin is proportional to the amount 

 of ferment present (76), as would be expected if the enzyme acted upon 

 the substrate through the formation of an intermediate compound accord- 

 ing to Guldberg and Waage's mass-law ; but this proportionality only 

 holds good within circumscribed limits of subtrate, enzyme, and hydrion 

 or hydroxidion concentration (77). My own experiments upon the 

 hydrolysis of casein by trypsin (78) enable me to confirm these state- 

 ments. 



In another field, that of toxins and anti-toxins, and of allied sub- 

 stances, the Guldberg and Waage mass-law has been applied with 

 considerable success, particularly byArrhenius and Madsen (79) ; never- 

 theless objections have been raised, find, although many of these objections 

 obviously arise from a misapprehension of the physico-chemical factors 

 involved, we may nevertheless consider it highly probable that the 

 principle of Guldberg and Waage's mass-law can only be applied to the 

 toxin-antitoxon reaction, as to the ferment reactions which I have 

 mentioned, under certain definite conditions. The facts appear to indi- 

 cate that those instances in which the simple laws hold good are particular 

 cases, under limiting conditions, of more general laws. In this con- 



