NATURAL HISTORY STUDIES 



It is the seat of continuous chemical changes 

 oxidations and reductions, hydrations and fermen- 

 tations which we sum up in the technical term, 

 metabolism. There is no doubt that the production 

 of light is one of the results of this metabolism. 

 Just as heat is produced by the activity of the 

 muscles and by all the combustions that go on in the 

 body, so light is produced in connexion with other 

 chemical processes involved in living. Many facts 

 point to the conclusion that the luminescence need 

 not be in itself of any vital importance, any more 

 than the heat produced in the active brain is nor- 

 mally of any importance, any more than the beautiful 

 colour of some organic waste products is in itself 

 of any importance. But just as the production 

 of heat or of pigment may be turned to good account 

 and made vitally important, so it may be with 

 the production of light. 



The facts in regard to luminescence in organisms 

 raise many unanswered questions and demand 

 further investigation, but there is no particular 

 difficulty about the bare fact that light is produced 

 in living cells. For it is the prerogative of living 

 cells to change energy from one form to another. 

 We know that in our own living laboratories heat 

 is produced. We know that electricity is generated 

 in the living laboratories of the Electric Eel or the 

 Torpedo. The production of light is just another 

 instance of transformation. 



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