Digestion — Ferments 103 



as food. Many fermentations involve oxidation, all of 

 which are destructive of food value. 



(Several theories have been advanced to account for 

 the action of the organized ferments. The most plausi- 

 ble seems to be that these little plants use sugar 

 and other compounds as food, deriving energy there- 

 from, the carbonic acid, alcohol and other new bodies 

 being the by-products of this use. Whatever may be 

 the real explanation of the changes that occur, fer- 

 mentations due to plant growth are among the most 

 useful agencies with which the farmer deals, and may 

 be the most harmful. 



There is another class of ferments which is termed 

 unorganized, and to which the general name enzym is 

 given. These are the ferments especially important in 

 digestion. They are merely chemical compounds which 

 produce a peculiar effect upon certain bodies with which 

 they come in contact. If a thin piece of lean beef be 

 suspended in an extract from the mucous lining of a 

 pig's stomach, to which has been added a small pro- 

 portion of hydrochloric acid, the liquid being kept at 

 about 98° F., the beef will soon begin to soften, after- 

 wards swell to a more or less jelly-like condition and 

 finally dissolve. The same general result would occur 

 with fish, blood fibrin or the coagulated white of an 

 Qg^. When starch, which is not affected by pure, warm 

 water, is placed in a warm water solution of crushed 

 malt it soon dissolves, leaving a comparatively clear 

 liquid. A chemical examination of these preparations 

 will reveal the fact that the compounds of the meat 

 are present in solution in somewhat modified forms, 



