76 EXPERIMENTAL OBSERVATIONS ON 



the reaction incomplete. It was found that the position of this 

 point of rest altered with the same factors as have already been 

 described as causing an alteration in Tammann's experiments, 1 

 viz. alteration of concentration of substratum ; alteration of con- 

 centration of enzyme ; alteration of concentration of the system 

 as a whole ; removal of products of reaction ; and alteration of 

 temperature. 



A certain amount of evidence in favour of the reversibility 

 of the reaction was. obtained by subjecting a 40 per cent, solution 

 of the products of reaction of caseinogen and trypsin to the 

 action of fresh trypsin, when in a period of four days a considerable 

 diminution of conductivity was observed, which is the reverse 

 of the increase in conductivity observed when the caseinogen is 

 acted upon, and is presumptive evidence that the reaction was 

 proceeding in the reverse or synthetic direction. 



Bayliss, in discussing the interpretation of his results, expresses 

 the opinion that the mode of treatment by E. F. Armstrong given 

 at length above, meets the case of trypsin better than any other, 

 and quotes verbatim the four cases given by Armstrong. 



In experiments upon the effects of alterations in the concentra- 

 tion of the trypsin, Bayliss found (1) that in the initial stage of 

 the reaction the velocity is in linear proportion to the amount 

 of enzyme, but (2) that this relationship is more and more de- 

 parted from as the reaction proceeds, so that a stage is eventually 

 reached at which the velocity is practically identical for different 

 amounts of trypsin. The explanation of the equality of rate of 

 change given is, that as the concentration of the substratum 

 diminishes there will come a time when there is only sufficient 

 for a small amount of enzyme to combine with and hydrolyse. 

 If the amount of enzyme present is not very small there will be 

 sufficient of it, in all the cases with the varying amounts, to act 

 upon all the available substratum. 



The following is a summary of other important results recorded 

 by Bayliss in this valuable paper : 



The velocity of reaction is proportional to the concentration of 

 the substratum up to about 4 per cent, in caseinogen ; above this 

 and up to about 8 per cent, it is independent of the concentration, 

 and above 8 per cent, it is inversely proportional to it. In no case, 



1 See p. 65. 



