EXPERIMENT STATION BULLETINS. 



353 



oxygen supply, light, etc., must remain constant in order to give com- 

 parable data. 



In speaking of ''fermentation cui'ves" from the one view point and 

 "enzymic curves" from the other, it is not intended at all to oppose the 

 general conception that probably all fermentations are caused by 

 enzymes. The word "fermentation" is used in its widest meaning as a 

 decomposition caused by micro-organisms, while the term "enzyme" is 

 applied to the chemical compound enzyme which, independent of the 

 cell, acts but does not multiply. It is really a distinction between 

 the organized and unorganized ferments of forty years ago, when it 

 was not known that the unorganized ferment is a product of the organ- 

 ized. 



The difference can be demonstrated quite plainly by the following 

 example: A drop of a pure culture of a liquefying bacterium is spread 

 over the surface of sterile gelatin in a test tube. The amount of lique- 

 faction is measured daily and recorded in millimeters. A three-days'-old 

 gelatin culture of the same organism is shaken with xylol for an hour to 

 kill all bacteria, and 1 cc. of the liquefied part is transferred into a test 

 tube with gelatin of the same diameter as the above culture; the lique- 

 faction is measured daily. In the first tube, we have a fermentation, 

 i. e.,* decomposition of gelatin by an organism, in the second, we have 

 enzymic action, all bacteria being killed. In an experiment with 

 Bacillus suMilis, the following data were obtained: 



Fig. 5. Gelatin Liquefaction hy Living and Dead Bacteria. 

 45 



