496 History of Luminescence 



could be removed from the wood, part of which was CO2. Des- 

 saignes tried extracting pieces of phospliorescent and non-phospho- 

 rescent wood with solvents and applied various tests to the extracts 

 to find out what changes took place. He also studied luminous fish. 



During the entire period of light production by fish there was 

 no trace of decomposition and no change in the muscle fibers. Only 

 the outer slime changed, becoming more turbid and opaque (but 

 always before decomposition) , and could be precipitated as a grayish 

 powder. Dessaignes studied the effects of temperature, distilled 

 water, alcohol, ether, many salt solutions and other agents on both 

 fish and wood, obtaining results, difficult to understand in 1809, but 

 easy to explain with modern knowledge that the light is due to 

 luminescence of bacteria. 



Dessaignes demonstrated the production of CO2 and showed that 

 the time the light lasted in a vacuum depended on the amount of 

 " bound air." In a " crucial experiment," he found that lumi- 

 nescent material from fish suspended in sea water entirely filling a 

 closed vessel soon lost its luminescence but the introduction of an 

 air bubble would call forth the luminescence again. 



From such facts Dessaignes concluded that spontaneous phospho- 

 rescence was a kind of burning whereby water and COo were formed. 

 The wood molecules did not appear to change but the luminous 

 substance, " un sue glutin-extractif," responsible for the phospho- 

 rescence was connected with the slimy binding material (undoubt- 

 edly the fimgus mycelium) of the wood fibers and disappeared 

 during a process that Dessaignes described as a fermentation, some- 

 thing like the retting of hemp. In animals also the light substance 

 was not the muscle fibers but appeared to be a slimy albuminous 

 sap (sue albumino-muqueux) that absorbed oxygen and became 

 continually more sticky and finally turbid. Dessaigne's comparison 

 with fermentation came very near the modern conception of lumi- 

 nescence as an enzymic process. Most of his ideas were quite good, 

 but he unfortunately missed the presence of luminous fungi or bac- 

 teria which would have removed the luminescence of wood and fish 

 from consideration in his prize essay. 



Placidus Heinrich, also, had the right idea in his views on lumi- 

 nous wood. Forty-two pages of the third Abteilung of Die Phospho- 

 rescent der Korpcr (1815) are devoted to luminous stumps, logs, 

 timbers, and roots. Like others he was somewhat mystified by the 

 fact that the beautiful light was so infrequent, and that it lasted so 

 short a time. Heinrich listed dampness and prevention of the free 

 access of air as absolutely necessary conditions for luminescence and 

 stated that the light did not arise in the fibers but in the binding 



