Shining Fish, Flesh, and Wood 487 



Effect of Gases on Shining Wood and Flesh 



With the recognition and separation of various kinds of gas at 

 the end of the eighteenth century, it was only natural that the action 

 of these new substances should be tested on shining wood, fish, and 

 flesh, i. e., on what were called " spontaneous phosphorescences," to 

 distinguish them from the phosphors that had to be excited by a 

 previous exposure to light. The element phosphorus was also classed 

 as a spontaneous phosphorescence and was frequently studied at the 

 same time as luminous wood (see Chapter XIII) . 



Between 1783 and 1800, seven papers dealing with the effect of 

 gases on luminous wood appeared, by F. C. Achard (1753-1821), 

 L. Spallanzani (1729-1799), G. Carradori (1758-1818), N. Tychsen 

 (1751-1804) , A. von Humboldt (1769-1859) , C. F. Gaertner (1785- 

 1829), and C. W. Boeckmann (1773-1821). An eighth paper by 

 N. Hulme (1732-1807) treated both wood and fish, particularly the 

 latter. All the investigations by authors of four nationalities, were 

 definitely experimental, published in chemical or physical journals, 

 their purpose to elucidate the cause of the luminescence and to 

 point out its relation to other light emitting processes, particularly 

 that of phosphorus. They will be treated in some detail since they 

 represent an important epoch in the history of bioluminescence. 



FREDERIC achard 



The first article by Achard, a director of the physical section of 

 the Berlin Academy, appeared in 1783. It was entitled " Experi- 

 ences sur le Bois Pourri Luisant," and described thirty-one experi- 

 ments, designed to discover the origin of the light of decaying wood, 

 although no conclusions were drawn. Achard collected wood in dif- 

 ferent degrees of putrefaction and observed that to be luminous it 

 must be rotten but not too rotten, that is not actually spongy— the 

 fibers must be coherent. He discovered that the luminous wood 

 could be dried, when the light would go out, but that it reappeared 

 on moistening; that the luminosity would remain under water and 

 also in a vacuum of 27^ inches ^^ and in dephlogisticated air ^'^ 



(O2) and inflammable air (Ho) ,^^ but in nitrous air (from action 

 of HNO3 on Fe) the light disappeared quickly, and in fixed air 



(CO2) it disappeared after one hour. Since the light of Kunkel's 



36 Very little oxygen is necessary to support luminescence. Enough remains in par- 

 tial vacua and also in nitrogen and hydrogen unless specially purified. 



^' During his study of the glowworm, Forster (1782) noted that luminous wood 

 became no brighter in dephlogisticated air (O2) , than in ordinary air. 



