THE PANCREA TIC ENZ YMES. 339 



states that pancreatic diastase is capable of converting 40,000 times 

 its weight of starch into maltose and dextrin ; Kroger, that 1 grm. of 

 pancreatic juice, containing 0'021 grm. of dry solid, of which in turn 

 only a small fraction could be amylopsin, digested in half an hour 4'67 

 grins, of starch. 



Influence of temperature. The rate of conversion increases with 

 rising temperature from C. to 30 C.; from 30 C. to 45 C. the rate 

 is at a maximum and practically constant. Above 45 C. the action 

 becomes slower with rising temperature, and ceases between 60 C. and 

 70 C., the ferment being here destroyed. 1 



Influence of reaction. Pancreatic diastase closely resembles salivary 

 diastase in its behaviour to change in reaction of the medium in which 

 it is dissolved. It seems to act best when neutralised or in presence 

 of minute traces of acid ; but a limit of acidity is soon reached beyond 

 which the rapidity of action rapidly diminishes, and the enzyme itself 

 is quickly destroyed. 2 The optimum activity, according to Melzer's 

 measurements, coincides with the presence of O'Ol per cent, of hydro- 

 chloric acid. 



Pialyn. Very little is known of the fat-splitting enzyme, pialyn, of 

 the pancreatic juice. That the action is due to an enzyme is shown 

 by the following experimental observations : (a) The action is de- 

 stroyed when the pancreatic juice or active pancreatic extracts are 

 boiled ; (&) it takes place in presence of antiseptics, and hence cannot 

 be due to bacteria. 3 



The enzyme is much less stable than either of the other two 

 associated with it in pancreatic juice. It is especially susceptible to 

 the action of acids, being quickly destroyed by all except the higher 

 fatty acids, so that great care to avoid acidity of solution must be 

 exercised in the preparation of it from the pancreas. Paschutin 4 

 recommends for its extraction a dilute solution of sodium carbonate 

 and bicarbonate in water, and Griitzner 5 that it should be extracted 

 from the perfectly fresh pancreas with a solution containing 90 c.c. of 

 glycerin to 10 c.c. of 1 per cent, sodium carbonate, ten times the weight 

 of gland to be extracted being taken of this fluid. However extracted, 

 it must l)e taken from a fresh gland and not from one which has stood over 

 a day, as in the case of the other two enzymes, for thereby an acid reaction 

 would be developed, and as a consequence the fat-splitting enzyme would 

 be destroyed. 



The rapidity of action of the enzyme is at first increased by rising 

 temperature. It acts almost twice as fast at 38 C. as at 18 C., but it 

 is destroyed by boiling ; the temperature of destruction is not accurately 

 known. 



It acts more slowly in the presence of 0'25 per cent, of sodium 

 carbonate than in neutral solution. 



Its activity is greatly increased by the presence of bile, still more 

 by a mixture of bile and hydrochloric acid ; this increase in activity is 

 due to the bile salts or bile acids, which have a similar effect. The 

 rapidity of action of the enzyme is usually much underrated, and it 



1 Roberts, " Digestion and Diet," London, 1891, p. 74 ; Proc. Roy. Soc. London, 1881, 

 vol. xxxii. p. 145. 



- Melzer, Inaug. Diss., Erlangen, 1894. 



3 Nencki, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1886, Bd. xx. S. 367. 



4 Arch.f. Anat. u. PhysioL, Leipzig, 1873, S. 386. 



5 Arch. f. d. ges. PhysioL, Bonn, 1876, Bd. xii. S. 302. 



