4i8 SCIENCE PROGRESS 



by the electromotive force and the hydrolysis of sugar. A 

 relationship between the H* ion concentration and the state of 

 the substrate has already been referred to. 



Groll (191 8), on the other hand, after showing that cations 

 retarded in a definite order — NH4>K>Na>So>Ba — came to 

 the conclusion that the action was similar to floccing ^ and other 

 colloidal phenomena, and considered it possible that the 

 influence of neutral salts is due to the fact that the dispersity 

 of the enzyme is modified by the ions in the same way as other 

 colloids. The similar suggestion put forward by Bayliss earlier 

 has already been referred to. 



It appears likely that amino-acids — which will be seen later, 

 under " Effect of Products," to assist the action of some enzymes 

 — act by an amphoteric electrolytic dissociation, i.e. they dis- 

 sociate with the formation of H* and OH* ions, and are capable 

 of acting either as acids or alkalies. 



The effects of different salts are more difficult to explain, 

 as there is added the complication that protoplasmic activity 

 may necessitate an antagonistic action of salts for its efficient 

 action. Such a necessity is seen in the influence of sodium, 

 calcium, and potassium on the heart. Falk (191 8) found that 

 weak solutions of sodium chloride might slightly stimulate 

 lipase but calcium always inhibited its action, and the effect 

 of the latter salt could always be counterbalanced by sodium 

 chloride. He noted also that this antagonism was of a definite 

 stoichiometrical order. In plant life Robbins (19 16) had 

 shown that the addition of chlorides and sulphates of alkalies 

 and alkaline earths diminished the amount of starch digested 

 by certain fungi, while nitrates caused an increase. Salts 

 have also an influence on the products formed in a reaction. 

 Koslechev and Frey (191 6) showed that zinc chloride causes 

 the production of acetic aldehyde in hefanol and dry yeast, but 

 not in living yeast, and only in the presence of sugar, while the 

 quantity of CO2 produced exceeds that of alcohol. Sub- 

 sequently in conjunction with Zabkova he showed that this 

 fact depended on the zinc ion. This appeared to be specific as 

 it was not given by other metals. Similarly in the fermentation 

 of sugar, mannite, and glycerine by bacteria, Neuburg and 

 Nord (19 1 9) showed that in the presence of sodium or calcium 

 sulphite acetaldehyde was formed ; or again, only certain 

 functions of the enzyme may be influenced as in the case of 

 calcium or the starch-liquefying enzyme of aspergillus oryzaie. 

 In this, Kita (191 8) found that calcium accelerated the lique- 

 fying action of the enzyme but not the saccharising action. 

 As there are so many factors involved in each individual case, 

 the problem is a very difficult one, and much of the tangle of 



1 Called "flaking" by Groll. 



