Shining Fish, Flesh, and Wood 497 



material, which by decomposition liberates water, carbon, and phos- 

 phorus. These then burn slowly. 



Like those of his predecessors, many of Heinrich's experiments 

 had to do with the effect of various fluids and gases. He found that 

 the light lasted longer in oxygen than in air and longer in a free 

 than in a closed space; also that luminous wood placed in a closed 

 vessel over water produced only a negligible change in volume. This 

 was correctly explained as the result of the formation of as much 

 new gas as was removed by the wood. 



Heinrich's final conclusion was that this spontaneous luminescence 

 came from " decomposition of the sap and of the fluid constituents 

 of the wood ... an extremely weak combustion taking place in a 

 minimum amount of air." Phosphorus was believed to play an im- 

 portant role since it is widespread in plants. He held that both 

 phosphorescent wood and fish were similar and might be considered 

 " the simplest, the most natural, and the most instructive of the 

 pyrophors " (Luftziinder) . Despite the fact that Heinrich men- 

 tioned luminous mushrooms as examples of other luminous vegeta- 

 tive growths, he failed to see a possible relationship between them 

 and luminous wood. 



G. R. Treverinus (1818, 1831) was undoubtedly influenced by 

 Heinrich's views, for he also believed that luminous material of 

 organized beings, which was obviously secreted by many living ani- 

 mals, was true phosphorus {wirklicher phosphor) or a material 

 having all the properties of true phosphorus. 



The " phosphorus origin " of luminous wood and fish appears to 

 have been generally accepted in the first half of the nineteenth cen- 

 tury. For example, the gi^eat Justus Liebig (1803-1873) , leader in 

 biochemical thought of the period, in his 1839 paper *^ on " Garung, 

 Faulniss und Verwesung," attributed the light of wood to oxidation, 

 and the light of fish to a phosphorus compound like phosphine, set 

 free during the decomposition of the flesh. This " chemical " point 

 of view was quite in line with his general ideas regarding the bio- 

 logical processes of fermentation and putrefaction, as indicated in 

 the next section. 



Finally, as the mid-century approached, the opinion of a distin- 

 guished biophysicist is of interest, that of Carlo Matteucci (1811- 

 1868) of the University of Pisa, whose luminescent studies had 

 previously been on the firefly. Matteucci (1849) made observations 

 on luminescent fish along the Mediterranean in 1847, finding that 

 the light " persisted a long time without decrease " in intensity in 

 hydrogen, nitrogen, and carbon dioxide containing " no trace of 



*''J. Liebig, Ann. der Physik (2) 18: 106-150, 1839. 



