100 INFLUENCE OF VARIOUS AGENCIES 



due to the hydrogen ion; thus organic acids solutions, such as 

 acetic, which are only ionised to the extent of two or three per 

 cent., have a correspondingly weak destructive effect, while in- 

 organic acids, such as hydrochloric, which in dilute solution are 

 almost completely ionised, break up the enzymes with great 

 rapidity. 



The degree of resistance as compared in different ferments is 

 subject to wide variation, dependent doubtless upon the chemical 

 constitution of the different enzymes, and arising usually from 

 the environment in which the enzyme has been developed. The 

 most exceptional enzyme in this respect is pepsin, which is most 

 active in a concentration of acid (i.e. of hydrogen ion) which 

 would be almost instantly destructive to nearly all other enzymes. 



The great majority of enzymes are produced and act in media 

 of alkaline reaction, and although in certain instances it has been 

 shown that even in the case of these ferments the degree of activity 

 is increased by a slight decrease in hydroxyl ion and increase 

 in hydrogen ion beyond their usual normal reaction, there is no 

 doubt that they act well in fluids of alkaline reaction, and accord- 

 ing to some observers are at their maximum activity in such media. 



While there is no doubt that all the enzymes occurring in 

 alkaline media in the body are quickly paralysed in their action 

 and rapidly destroyed by more than the merest trace of free acid, 

 and also, that a slight trace of. free alkali above the amount necessary 

 to form bicarbonate with the carbonic acid present has a similar 

 effect ; there is much difference of opinion in the literature of the 

 subject as regards the point of optimum action of each ferment. 

 The subject is made very hazy by the fact that earlier workers, 

 not realising that the all-important point was the concentration 

 in the solutions tested of the hydroxyl and hydrogen ion, have 

 worked indiscriminately with free alkalies in some cases and 

 carbonates in others. Kanitz, 1 who is one of the more recent 

 workers on the subject, has examined the effect upon the activity 

 of trypsin of different alkaline hydrates and carbonates, and states 

 that the action is dependent upon the concentration of the 

 hydroxyl ion, and that the range of greatest activity lies between 

 Tb-YtJo normal. 



It is interesting to observe that the same effect of acids and 



1 Zeitsch.f. physiol. Chem., 1902, vol. 37, p. 75. 



