206 THE DIASTATIC ENZYME. [BOOK II. 



Temperature Roberts has found that the action of pancreatic 

 dia " diastase on starch mucilage increases in speed from 



ofpancrTa^is zero . to 30 - From this ^ 45 C - the rate of action 



most active. continues steady. Above 45 the action becomes slower 



and slower, and ceases between 60 and 70. 



Rapidity of ._ . 



action of a so- We have seen that within a certain range of tem- 



lution contain- perature the rapidity of the action upon starch increases, 



ing the diasta- Temperature and all other conditions being exactly 



tic ferment m- sim ii ar the rap idity of the action will depend upon the 



fluenced by the .. c mi 



amount of fer- quantity of enzyme present. This is well brought out 



ment. in the following remarks 1 . 



' The speed at which a given quantity of starch is transformed by 

 diastase depends essentially on the proportion of ferment brought to act 

 upon it. In the above experiments (experiments in which a minimal 

 quantity of diastatic solution acted upon starch) the proportion of diastase 

 was very minute in comparison with the amount of starch, and the action 

 went on slowly for forty-eight hours. But if we reverse these proportions 

 and mix a small amount of starch with a large amount of diastase the 

 transformation is instantaneously accomplished. If a test-tube be half 

 filled with an active extract of pancreas and a few drops of starch mucilage 

 be quickly shaken therewith, you cannot detect the reaction of starch or 

 dextrine in the mixture, however prompt you may be with the testing 

 the transformation has followed on the admixture as instantaneously as 

 the explosion of the charge follows the fall of the trigger. Between these 

 extremes there are all gradations.' 



Estimate of Roberts has estimated that pancreatic diastase is 



the activity of a kl e to transform into sugar and dextrin no less than 

 ^ r e men i t astatic 40,000 times its own weight of sugar 2 . 



Roberts has compared by his method of diastasi- 



Estimate of me try (see chapter I. p. 56) the diastatic activity of 

 the amount of > , / ,1 p , i i i .j 



ferment pre- t ^ ie tissue * the pancreas of the ox, sheep, and pig, and 



sent in the he finds that the ferment contained in 1 gramme of 

 pancreatic tis- the fresh pancreas of the pig can convert 5 grammes of 

 sue of the pig, dry starch into products which give no colour reaction 

 ox and sheep. w ^ J Q( J j ne . the same weight of the pancreas of an ox 

 would only act in a similar manner upon 0'4 grm. of starch ; and 

 the same weight of the pancreas of the sheep would act upon 0'44 

 grm. of starch. 



Is there a Zymogen of the Diastatic Ferment ? 



In giving the history of the proteolytic ferment of the pancreas 

 trypsin abundant anatomical and experimental evidence will be ad- 

 duced to prove that there exists in the secreting cells of the pancreas 

 a body from which the ferment is derived ; this body from which the 



1 Koberts, Lumleian Lectures, page 40. 



2 Roberts, op. cit. p. 39. 



