Physiologie. 139 



Armstrong, E. F. and R. J. Caldwell, S tu dies in Enzyme 

 Actio n. IV. The Siicrociastic Action of Acids as 

 contra sted withthat of Enzyme s. (Proc. Roy. Soc. 

 London. July 7, 1904.) 



An extract of lactase mixed with sufficient milk-sugar to 

 give a 5°/o Solution will Hydrolyse about "^/s of the sugar at 

 35*^ C. in about an hour, whereas it takes twice normal Hydro- 

 chloric acid at the same temperature about 5 weeks to effect 

 this amount of hydrolysis. In spite of the generally enormous 

 difference in the rates at which enzyme and acid effect hydro- 

 lysis, a similar explanation may be given, based on the 

 assumption of an active-mass System as described in a pre- 

 vious paper. The active mass consists of part of the enzyme 

 combined with part of the acid. The water is regarded as 

 attracting both sugar and acid molecules, and at any tempe- 

 rature equilibrium is set up between water, sugar and acid, 

 depending on their relative proportions. 



A change in quantity of any one of them will upset the 

 equilibrium and therefore also the active mass. If a proportion 

 of acid in some degree corresponding to the proportion of 

 enzyme commonly used be employed there is reason to think 

 that a linear period would be found, equal quantities of 

 sugar being hydrolysed in successive equal intervals of time, 

 the logarithmic lav/ being obeyed only in the later stages. 

 Adding more acid increases the rate of hydrolysis disturbing 

 the equilibrium in the direction of increasing the magnitude of 

 the active System, the sugar apparently being a greater gainer 

 than the water. An increase in the amount of sugar must 

 diminish the attraction exerted by the water on the acid and 

 hence the active-mass will increase. Any substance having an 

 affinity for water should act similariy and it is well known that 

 the hydrolysis of cane-sugar is hastened by the presence of 

 neutral salts. In the case of hydrolysis by acids the products 

 accelerate the rate of change (instead of retarding it as pre- 

 viously described for enzyme-action) in the same manner as 

 the addition of a neutral salt. Rise in temperature accelerates 

 greatly the rate of hydrolysis, probably by causing rapid break- 

 down of the active System. 



The differences between enzyme- and acid-hydrolysis are 

 probably due to the superior affinity of enzyme for carbo- 

 hydrates, and to the very different behaviour of the two classes 

 towards water in consequence of the colloid nature of the one 

 and the crystalloid nature of the other. e. Drabble (London). 



Armstrong, H. E., Enzyme Action as bearing onthe 

 Vaiidity of the lonic-Dissociation Hypothesis 

 and on thePhenomena of Vital Change. (Proc. 

 Roy. Soc. London. July 7, 1904.) 



The author urges the advisibility of recognising the part 

 played by phenomena of „association" in chemical change and 



