130 THE NATURE OF ANIMAL LIGHT 



completely oxidized by boiling or standing in air until it no 

 longer gives light with lucif erase) if mixed with a sus- 

 pension of ground frog's muscle and kept in a well-filled 

 and stoppered test tube for some hours, is reduced to 

 luciferin and gives a bright light if now poured into 

 luciferase solution. Frog muscle suspension alone, or 

 oxyluciferin alone, give no light with luciferase, nor will 

 a mixture of frog muscle suspension and oxyluciferin, if 

 shaken with air for several hours. Only if this last mix- 

 ture be kept under anaerobic conditions is the oxylucif- 

 erin reduced. 



The reducing action of tissues is said to be due to a 

 reducing enzyme (reducase or reductase) y itself composed 

 of a perhydridase and some easily oxidized body such as 

 an aldehyde. In the presence of the perhydridase the 

 oxygen of water oxidizes the aldehyde and the hydrogen 

 set free reduces any easily reducible substance which may 

 be present. There is a perhydridase in fresh milk, spoken 

 of as S char dinger's enzyme, which is destroyed by boil- 

 ing. If some aldehyde is added, fresh milk will reduce 

 methylene blue to its leuco-base or nitrates to nitrites, 

 upon standing a short time. If shaken with air the blue 

 color returns. There is no reduction unless an aldehyde 

 is added or unless some boiled extract of a tissue such as 

 liver is added. The boiled-liver extract has no reducing 

 action of its own, but supplies a substance similar to the 

 aldehyde which has been spoken of as co-enzyme. The 

 aldehyde is oxidized to its corresponding acid. Milk will 

 reduce methylene blue without aldehyde if bacteria are 

 present in large numbers. There is no reduction if the 

 milk, methylene blue, and aldehyde are agitated with air. 

 The temperature optimum is rather high, 60° to 70° C. 



