METABOLISM 61 



are apparently responsible for the oxida- 

 tion of alcohol to acetic acid in the pro- 

 duction of vinegar as well as for changes 

 in color and flavor in the curing of to- 

 bacco and tea. They are also active in 

 producing famous Tyrian purple of the 

 Romans, obtained from a shellfish. 



The production of light by lumi- 

 nescent animals and plants is due to oxi- 

 dation carried on by means of oxidizing 

 enzymes. This may be illustrated by an 

 interesting experiment in which the juice 

 of a potato or turnip (which contains 

 oxidizing enzymes) is mixed with pyro- 

 gallol (an oxidizable substance) in the 

 presence of hydrogen peroxide, which 

 furnishes oxygen. When this mixture is 

 made in the dark room a distinct lumi- 

 nosity is observed. 



While many of the oxidations of the 

 organism can be traced to more or less 

 definite enzymes others have not yet 

 been explained upon this basis. At pres- 

 ent we know very little of the various 

 steps in the process whereby food is 



