150 Dr. W. Roberts. Estimation of the Amylolytic [May 5, 



Table II. 



Experiments showing the postponement of the achromic point when 

 the action is protracted. The quantity of standard mucilage acted on 

 in each experiment was 10 cnb. centims. diluted with water up to 

 100 cub. centims. Temperature 40° 0. The " calculated " time in the 

 third column was obtained by taking the first observation, which was 

 several times repeated, as a standard of comparison. 



Quantity of pancreatic 

 extract employed. 



Time in which the achromic point 

 was reached. 



Found. 



Calculated. 



0*05 cub.centim. 

 -005 

 -004 

 -002 

 -0005 



10 minutes. 

 115 



140 „ 

 300 

 1,380 



100 minutes. 

 125 „ 

 250 

 1,000 



It need scarcely be said that when the enzymosis is very slow it is 

 not possible to fix the vanishing point of the colour reaction with the 

 same precision as when the action is more rapid and the change more 

 abrupt. Notwithstanding this source of error, I think the conclusion 

 indicated by the experiments may be relied on. The postponement of 

 the achromic point shown in the table may be explained, as has been 

 suggested, on the assumption that the enzyme liberates its energy at 

 a continually retarded rate. In the case of trypsin, we shall see 

 evidence of a precisely parallel phenomenon. 



Temperature. — The action of pancreatic diastase on starch mucilage 

 was found to increase in energy (or speed) from zero up to 30° C. 

 Erom this point to 45° the rate of action continued steady, showing a 

 range or platform of indifferent temperature extending from 30° to 45°. 

 Above 45 c the action became less and less energetic, and finally ceased 

 between 65° and 70°. The following table exhibits the results obtained 

 at various temperatures between 5° and 70°. 



Table III. 



Showing the effects of temperature on the action of pancreatic 

 diastase ; the amount of the standard mucilage acted on in each experi- 

 ment was 10 cub. centims. diluted with water up to 100 cub. centims. 

 The quantity of pancreatic extract employed in each experiment was 

 0'1 cub. centim. 



