ENZYMES AND OTHER FERMENTS DIGESTION. I 3 I 



attempts have been made to obtain a " pure " pepsin. The 

 strongest, that is the most active, products so secured have 

 been analyzed. The results do not differ greatly from those 

 found on analyzing the proteins, yet with some of these prod- 

 ucts it is not possible to obtain the ordinary protein reactions. 

 We have no clew to the real composition of the substance. 

 It is not at all diffusible through parchment and must have a 

 high molecular weight. 



It is stated above that pepsin and rennin are possibly iden- 

 tical substances. The view commonly held by the majority 

 of chemists and physiologists has been that they are distinct 

 ferments produced possibly by different regions of the stom- 

 ach, but in late years a mass of evidence has been accumulat- 

 ing which appears to throw doubt on this notion and suggest 

 the perfect identity of the two proteolytic enzymes. The 

 chemists of the Pawlow school have been particularly active 

 in advancing this theory. According to them an extract 

 which shows the digesting power will also show the milk 

 curdling action. If it is strong in the one case it will be found 

 strong in the other if the conditions are made right. This 

 amounts to saying that the same enzyme does the two kinds 

 of work, but the conditions of reaction, concentration, salt 

 content, etc., must be different in each case. A commercial 

 rennet, for example, if largely diluted with 0.2 per cent hydro- 

 chloric acid, will show a strong proteolytic reaction, while 

 without such dilution it may appear quite inactive. It is held 

 further 'that the milk curdling ferment of the pancreatic ex- 

 tract is probably identical with the trypsin to be now described. 



Trypsin. One of the most active and important of the 

 body ferments is the substance which occurs in the pancreas 

 and known as trypsin. It may be extracted from the minced 

 organ in a variety of ways and in crude form is a commercial 

 product. In its action it bears some resemblance to pepsin, 

 but works under different conditions. While pepsin digests 

 protein compounds in dilute acid medium trypsin is most ac- 

 tive in presence of weak -alkali, preferably sodium carbonate. 



