1881.] and Proteolytic Activity of Pancreatic Extracts. 153 



the amount of starch mucilage of known strength which can be trans- 

 formed by a unit measure of the diastasic solution to the point at which 

 it ceases to give a colour reaction with iodine, in a unit of time and 

 at a given temperature. 



In reducing this principle to a definite formula it was necessary to 

 choose arbitrarily a unit of measure and a unit of time. The unit of 

 measure fixed on was 1 cub. centim., and the unit of time 5 minutes. 

 These selections seemed, on the whole, the best adapted for furnishing 

 a convenient scale. On these bases the formula took the following 

 form : the diastasic value of any solution — or D — is expressed by the 

 number of cubic centimetres of the standard starch mucilage which can 

 be transformed to the achromic poinb by 1 cub. centim. of the solution 

 to be tested in a period of five minutes at a given temperature. 



In the process of testing the quantity of the standard mucilage was 

 made constant, namely 10 cub. centims., and the quantity of pancreatic 

 extract and the time were made variable. In order to get the value 

 of D the results must be so transformed as to make the quantity 

 of extract and the time constant, and the quantity of the standard 

 mucilage variable. This is accomplished by increasing or reducing the 

 quantity of pancreatic extract employed to 1 cub. centim., and in- 

 creasing or diminishing the standard mucilage in the same proportion. 

 The product thus obtained is again increased or reduced in the same 

 proportion as is requisite to increase or reduce the time found to five 

 minutes. Taking the example above given, the value of D is obtained 

 by the following formula : Let p signify the quantity of pancreatic 

 extract employed, and m the number of minutes required to reach the 

 achromic point, then : — 



p m 



:a,nd in the above example — 



D=i5-x^=83 at 40° C. 

 0-1 6 



The value of D, as already explained, signifies the number of cubic 

 centimetres of the standard starch mucilage which can be changed to 

 the achromic point by 1 cub. centim. of the diastasic solution in five 

 minutes at a given temperature. As the standard mucilage contains 

 1 per cent, of dry starch, the value of D divided by 100 gives us the 

 same value in terms of dry starch, and the result of the above experi- 

 ment may be read as follows : — 



B = 83 = 0-83 grm. of dry starch. 



This method of diastasimetry is equally applicable to saliva and 

 malt- diastase. It may also be applied to the estimation of the 



m 2 



