594 History of Luminescence 



detect radiant heat from Pyrophorus without success, thus estab- 

 lishing animal light as of high luminous efficiency. Quantitative 

 efficiency studies on a luminous bacterium, regarded as a power 

 house for producing light, were first made by E. N. Harvey (1925) , 

 who found an " overall " efficiency about equal to that of an incan- 

 descent electric lamp. A single bacterium emitted about 2 X 10"^* 

 candle. 



Older workers referred to light intensity of luminous organisms 

 in terms of the ability to read fine print. The first actual measure- 

 ment appears to have been made by Dubois (1886) , who found 1/150 

 of a " Phoenix " candle of 8 to the pound, while Langley and Very 

 (1890) observed 1/1600 candle, both observers using the beetle 

 Pyrophorus. The first measurements on colonies of luminous bac- 

 teria were made by A. Lode (1904) , whose figure was 7 X 10"^° 

 international candle per square millimeter. 



That luminous animals require mechanical agitation or some kind 

 of stimulation in order to light must have been apparent to any who 

 observed marine forms. Von Humboldt, during his journey to the 

 equinoctial regions of the new continent in 1799-1804 observed that 

 a jellyfish on a pewter plate would luminesce by electrical stimula- 

 tion. Macartney (1810) also noticed the luminescence of jellyfish 

 on electrical stimulation, on heating, and on plunging into " spirits." 

 The first electrical stimulation of minute dinoflagellates responsible 

 for the light of the sea appears to have been made by Pfaff (1823) 

 at Kiel, and the first electrical stimulation of Noctiluca by Pring 

 (1849) or by Quatrefages (1850) . 



In 184.8 Quatrefages had observed that the light of small worms 

 and ophiuroids appeared when their muscles contracted, and he is 

 mostly responsible for a rather general idea in the late nineteenth 

 century that luminescence and contractility are related. Actually 

 there is no relation except that both luminescence and muscular con- 

 traction appear as a result of stimulation. 



It is difficult to ascribe the recognition that nerves can carry im- 

 pulses to a luminous organ to any one person. Spallanzani (1783) 

 and others noticed the waves of light which pass over a pennatulid 

 after stimulation by touching one part of the colony, although it is 

 doubtful whether it was recognized at that time that nerves were 

 involved in the transmission, and even Panceri (1870-1872) was not 

 sure the impulse was a nervous one. 



Many observers spoke of the will to flash on the part of a firefly 

 and Macaire (1821) showed that when the head was cut off and 

 the body connected to wires from a galvanic pile, light appeared on 

 making the current, but he did not speak of nerve control. A. W. 



