156 PHOSPHORESCENCE OF ANIMALS. 



many other kinds of creatures which, under certain 

 circumstances, become luminous in the dark. This is 

 always dependent upon vitality ; for all these animals, 

 when deprived of life, cease to shine. 



At the same time we have many very curious 

 instances of phosphorescence in dead animal and 

 vegetable matter ; the lobster among the Crustacea, and 

 the whiting among fishes, are striking examples ; 

 decayed wood also emits much light under certain con- 

 ditions of the atmosphere. This development of light 

 does not appear to be at all dependent upon putrefac- 

 tion ; indeed, as this process progresses, the luminosity 

 diminishes. We cannot but imagine that this light is 

 owing, in the first place, to direct absorption by, and 

 fixation within, the corpuscular structure of those bodies, 

 and that it is developed by the decomposition of the 

 particles under the influence of our oxygenous atmos- 

 phere. 



The pale light emitted by phosphorus in the dark is 

 well known ; and this is evidently only a species of slow 

 combustion, a combination of the phosphorus with the 

 oxygen of the air. Where there is no oxygen, phospho- 

 rus will not shine ; its combustion in chlorine or iodine 

 vapour is a phenomenon of a totally different character 

 from that which we are now considering. This phos- 

 phorescence of animal and vegetable matter has been 

 regarded as something different from the slow combus- 

 tion of phosphorus; but, upon examination, all the 

 chemical conditions are found to be the same, and it is 

 certainly due to a similar chemical change. 



The luminous matter of the dead whiting or the 

 mackerel may be separated by a solution of common 

 salt or of sulphate of magnesia ; by concentrating these 

 solutions the light disappears ; but it is again emitted 

 when the fluid is diluted. The entire subject is, how- 

 ever, involved in the mystery of ignorance, although it 

 is a matter quite within the scope of any industrious 



