PHYSIOLOGICAL LIGHT. 



By Raphael Dubois, 



Professor of General and Comparative Physiology in the Faculty of Sciences at Lyons. 



Part First. — Photogenic Organisms. 



One of the most curious phenomena of life is unquestionably the 

 property possessed by certain organisms of radiating into space, as 

 luminous vibrations, a part of the energy that animates them. It might 

 be said that these vibrations are those of life itself, since they emanate 

 from a living substance that dies in generating them. This light being 

 physiological in its origin, I have called its production the photogenic 

 function. Its study comprises one of the most interesting and most 

 important chapters of general physiology — that branch of science 

 which embraces the history of the phenomena of life common to ani- 

 mals and vegetables. 



I. 



The existence of the photogenic function has been demonstrated de 

 visu in numerous species belonging to the two kingdoms, and it might 

 perhaps be found in all living creatures if we possessed instruments of 

 sufficient delicacy to detect it; but this is pure hypothesis. 



In vegetables this function has been observed with certainty only in 

 organisms destitute of chlorophyll or, occasionally, in parts deprived of 

 the chlorophyll-making function (the yellow flowers of the French and 

 African marigolds, of the nasturtium, and others of the same color), aud 

 therefore corresponding closely with animals as to their general nutri- 

 tion. But it is only in mushrooms and white algse that the photogenic 

 function has been studied in a truly scientific manner. 



The family of Bacteriacece includes many photogenic species, both 

 marine and terrestrial, that form the geniis Photobacterium. The 

 marine Photobacteriacew live free in the sea or on the surface of fishes, 

 crustaceans, cephalopods, and many other animals; but they do not 

 generally become luminous until after the death of their host, and after 

 being out of the water from twenty-four to thirty-six hours. As soon 



1 Translated from the Revue Gene"rale des Sciences pures et appliquees, June 15> 

 and July 30, 1894, Vol. V, pages 415-422 and 529-534. 



413 



