vm] RENNET AND ITS ACTION 139 



stomach, is also unknown. Finally, it may be men- 

 tioned that rennet, or a rennet-acting substance, is 

 produced by numerous bacteria. 



Active Principle of Rennet. While it has been 

 found impossible hitherto to isolate rennet in an 

 absolutely pure condition, Hammarsten (to whose 

 researches is due most of our information on the 

 nature of rennet, as well as its action) has obtained, 

 in a comparatively pure state, what he regards as its 

 active principle. To this he has given the name lab, 

 while the terms chymosin and pixine have also been 

 applied to it by other investigators. It belongs to 

 that class of ferments which are known as chemical 

 or unorganised ferments (also known as enzymes}, and 

 which have only been distinguished from the organised 

 ferments for about thirty years. To the same class 

 belong diastase, a substance which converts starch 

 into sugar, and pepsin, which dissolves the albu- 

 minoids. Both rennet and pepsin are found in the 

 gastric juices of the stomach, and both are to be re- 

 garded as digestive ferments of the highest import- 

 ance. These enzymes, or chemical ferments, are 

 produced by the growth of the organised ferments. 

 These two classes of ferments the true or living 

 ferment, and chemical ferment or enzyme are dis- 

 tinguished from one another by certain properties. 

 The former are insoluble in water, while the latter 

 are soluble. Again, while the chemical ferment can 



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