Animal Luminescence 549 



as other animals have the power of extracting from the same air, by a 

 chemical process, the fluid of heat." 



Like other workers of his time, Carradori did not realize how 

 small an amount of oxygen is necessary to cause the emission of 

 visible light from luminous organisms. In the later work of T. von 

 Grotthuss (1807, 1821), J. Macaire (1821), J. Murray (1826), and 

 C. Matteucci (1847) , it was correctly found that the light would 

 disappear in hydrogen, nitrogen, COo, or a good vacuum, and re- 

 turn in the air. In pure oxygen, Macaire, Murray, and Matteucci 

 observed a brighter light while Hermbstadt ^- (1808) and H. Davy ^^ 

 did not. Actually the effect of oxygen depends on the species of 

 firefly and time of exposure to the pure gas. 



EARLY NINETEENTH-CENTURY PHYSIOLOGICAL WORK 



The studies on lampyrids initiated by Forster, Beckerhinn, Spal- 

 lanzani, and Carradori were continued during the early part of the 

 nineteenth century by J. Macartney (1810) , M. Faraday (1814) , 

 Macaire (1821), Murray (1826), Carrara (1836), and Matteucci 

 (1843, 1844, 1847) . These men concerned themselves not only with 

 the effect of various gases and other substances on the luminous 

 material but also with habits, the " will " to flash, the efiFects of tem- 

 perature, and of electricity and galvanism. Macartney thought he 

 detected one or two degrees rise of temperature when a delicate 

 thermometer was brought near a glowworm, but was not sure and 

 his observations not well planned. 



John Murray said: " Light as connected with the glow-worm, is 

 a subtile evanescent material principle, perhaps connected with a 

 peculiar organized structure." 



At Geneva (July 10-12, 1814), Faraday^* determined that light 

 from crushed organs of the glowworm would last for several days and 

 concluded that this power " appears to depend more upon the chemi- 

 cal nature of the substance than upon the vital powers of the ani- 

 mal." The luminous matter 



is yellowish-white, soft and glutinous. It is insoluble apparently in 

 water or in alcohol. It does not immediately lose its power of shining 



1^ Hermbstadt (1808) collected 200 " Leiichtkafer " and put them in a flask. In 

 oxygen prepared from Braunstein (MnO,) , the luminescence was not much brighter 

 than in air but lasted longer. In hydrogen and nitrogen there was a very faint lumi- 

 nescence but none in carbon dioxide. 



^* According to Macartney (1810:287), Humphry Davy found that a glowworm 

 light " is not rendered more brilliant in oxygene . . . and that it is not sensibly 

 diminished in hydrogene gas." 



^* Life and letters of Faraday, Dr. Bence Jones, pp. 144-146, 1870. 



