ON ENZYMES AND LIVING CELLS 209 



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 according to 

 some observers are at their maximum activity in such media. 



While there is no doubt that all the enzymes occurring in alka- 

 line 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 indiscri minately with free alkalies in some cases and 

 carbonates in others. 



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

 alkalies, and the same dependence upon hydroxyl and hydrogen 

 ions, is observable in the case of living cells as has been described 

 above in the case of the enzymes. 



The rate of growth and cell division, and the regularity of 

 the latter process, are dependent in large measure upon the reac- 

 tion of the medium which bathes and permeates the cell. Solutions 

 of various neutral salts in addition have a marked influence upon 

 cell growth and upon the maintenance of a physiological condition 

 of normal metabolism in the cell, but it is the alkalies and acids, 

 and these proportionately to their concentration in hydroxyl and 

 hydrogen ions, which exercise the profoundest influence. 



A normal balance in the ratio of hydroxyl and hydrogen ions 

 must be maintained, or the whole of the metabolism and life of 

 the cell becomes abnormal and morbid. 



The position of pioneer in this subject must be ascribed, as 

 mentioned above, to Sidney Ringer, who first showed the enormous 

 importance of even minute doses of certain inorganic salts in 



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