44 PLANT PHYSIOLOGY 



11. 37-8, for In addition . . . hydrogen read 6. Glucoside-splitting enzymes 

 form grape sugar, in addition to other substances, from glucosides ; thus 

 amygdalin is split by emulsin into glucose, hydrocyanic acid, and oil of bitter 

 almonds. 



In each group of these enzymes there are several distinct types with quite 

 specific activities ; by these activities they have been characterized, and they 

 have been asserted to have a general capacity for splitting off oxygen from 

 H 2 O 2 . Apparently, however, in this we have to deal with an admixture of 

 another enzyme, of which we shall speak later. 



153, 11. 2-12, for platinum is ... inhibitory read platinum (i.e. platinum 

 particles of ultra-microscopic size in water) is, on the other hand, exceedingly 

 active. BREDIG (1901) has obtained such colloidal solutions by kathodic spray- 

 ing, and has shown that they exhibit close analogies with enzymes. The 

 fact that enzymes are colloids has not been previously mentioned, but that 

 they are so may be readily understood, since in all probability they are to be 

 classified along with proteids. In the second place, colloidal platinum acts 

 catalytically in quite minimum amount, just like an enzyme. BREDIG observed 

 catalysis of H 2 O 2 with a dilution of the platinum to 0-0000003 m g- P er cc m. 

 Thirdly, the analogy between the enzyme and a colloidal solution shows itself 

 in the fact that both are affected by substances which act poisonously bodies 

 known as ' paralysers '. 



11. 16-30, for BREDIG finds . . . 1892) read The chief point, however, is 

 the alleged similarity in the catalytic action of the enzyme and of the colloidal 

 platinum. This, according to BREDIG, lies in the fact that, in addition to acting 

 catalytically on H 2 O 2 , colloidal platinum can invert cane sugar and effect 

 other fermentative reactions occurring in the organisms, while, on the other 

 hand, enzymes, in addition to their own specific capacities, can induce a reduc- 

 tion of H 2 2 . We may leave it undecided whether really and truly colloidal 

 platinum may be said to have an enzymatic influence (comp. Zeitsch. f. phys. 

 Chem. 31, 212, note) ; we merely note that the H 2 O 2 -catalysis induced by 

 the enzyme is, as already stated, exceedingly problematical. By heating 

 up to a definite temperature (JACOBSON, 1892) the power of the enzyme to 

 catalyse H 2 O 2 becomes lost, while its own specific capacity remains unaltered. 



1. 33, for very obvious read probable 



1. 41 P. 154, 1. 42, for Further differences . . . 1902) read For all that, 

 BREDIG has gone too far in describing colloidal metallic solutions as inorganic 

 ferments. The similarity may possibly lie merely in the fact that both bodies 

 are catalytic agents. Mineral acids also, which operate hydrolytically, are 

 inorganic catalytic agents, and numerous instances of such acids are known. 

 Many of them accelerate very many reactions, while others have more limited 

 spheres of activity (examples are given by CZAPEK, Biochem. I, p. 59). Enz} r mes, 

 on the other hand, are characterized obviously by their eminently specific 

 functions, and in that fact lies their significance not only in the organism, but 

 also in physical chemistry. 



154, 1. 54, after at present, read If we describe the action of catalytic agents 

 by saying that they alter the rate of a reaction which takes place in their 

 absence, it is equivalent to saying that they are unable to effect the final result 

 of the reaction. The final result of a chemical reaction is, however, varied. 

 In many cases it results in a complete transformation of the initial substances 



thus cane sugar is entirely converted into glucose by means of acids. On 

 the other hand, there are reactions which cease when an equilibrium is reached. 

 Thus, for example, the splitting of the acetic ester into ethyl-alcohol and 

 acetic acid by taking up water is not carried to completion, but ceases before 

 all the ester is decomposed. This phenomenon is to be explained by regarding 



