1911.] The Properties of Colloidal Systems. 91 



I have shown* that this property gives an accurate estimate of the amount 

 of chemical change which takes place in a trypsin digest. The trypsin used 

 in most experiments was a preparation obtained from Hopkin and Williams, 

 occasionally an extract of pancreatin " Ehenania " was used. For dilution it 

 was thought necessary to make use of a boiled trypsin solution of the same 

 concentration as that to be diluted, since the electrolyte concentration would 

 be more nearly equal than if water were used. From the data thus obtained 

 curves were constructed, from which it was easy to obtain the time taken by 

 each flask to arrive at the same stage of the reaction. In many cases it was 

 possible to compare the times taken to reach the various steps, for example, 

 an increase of 1400, 2000, 3000, etc., recip. megohms in conductivity. The 

 velocities of the reactions being inversely proportional to the times taken to 

 effect a given change, the reciprocals of the values got from the curves were 

 calculated and multiplied by a number, usually 10 4 , in order to avoid 

 fractions. As would be expected, it was found that, not infrequently, two or 

 more. of the members of a particular experiment would show an anomalous 

 behaviour, easily detected on the curve and usually found to be due to 

 incipient putrefaction, although toluene was always added at the commence- 

 ment. In the tables below these values are placed in brackets. These tables 

 are given in order to show the kind of data obtained, Tables I and II from 

 two caseinogen experiments and Table III from one with gelatin as 

 substrate. No object would be gained by multiplying these tables, since 

 they serve to bring out the exponential law. The numbers under the head 

 of trypsin concentration are merely relative to one another. The highest, 

 called 256, is that of 2 c.c. of a 2-per-cent. solution, so that the lowest is 

 1/ 256th of this. 



Table I. 









Eeciproeal x 10 4 of time to effect change of 





Concentration 

















of enzyme. 



















1400. 



2000. 



30 



DO. 



4000. 



5000. 



1 





35-1 



1 -925 



1 



164 







2 



5 





2-78 



1 



518 







4 



7 



2 » 



4-265 



2 



36 



1 -573 



1-178 



8 



11 



58 J 



6-77 



3 



55 



1 -954 



1-335 



(16) 



(51 



35) 



(31 -25) 



(14 



3) 



(7-05) 



(3 -39) 



(32) 



(33 



33) 



(11 -8) 



(2 



73) 



(1 -22) 





64 



200 



1 



111-1 ] 



55 



55 



22 -24 



7-25 



128 



333 



3 IC 



200-0 \B 



124 



3 



52 -3 



32-4 



256 



500 



J 



400-0 J 



257 



1 



131 -0 



51 -45 



* ' Journ. of Physiol.,' 1907, vol. 36, p. 221. 



