ANIMAL AND VEGETABLE PHOSPHORI. 



Dead luminous Substancet. 



Light, as we have already observed, being more or less ab- 

 sorbed by bodies of all kinds, may be expected, under circum- 

 stances which tend to unite or aggregate its particles, to flow off 

 in a percipient form from all those which have absorbed it in a 

 greater degree, or retain it after absorption in a looser manner than 

 others. Thus it exists in the shells of marine-fishes, or testaceous 

 worms, and is set at liberty and flows off in a visible form after 

 calcination. It exists in the dead trunks of various vegetables ; 

 and hence, on the commencement of a putrefactive decomposition, 

 the particles unite together agreeably to the. laws of chemical affi- 

 nity, and flow off in like manner : whence the luminous appear, 

 ance exhibited in various species of rotten-wood. It exists largely 

 in the bodies of many kinds of animals, and more largely in some 

 animal organs than in others ; hence we see it issuing sometimes 

 from putrescent flesh, sometimes from bones, teeth, bezoars, 

 nephritic, and urinary calculi, and egg. shells that have been ex- 

 posed to the sun. 



In marine fishes it appears to be more accumulated than in the 

 bodies of any animals, though for want of appropriate luminous 

 organs these are not found to secrete it (at least not aggregately and 

 palpably) during life. 



For the best experiments we possess upon this subject we are 

 indebted to Dr. Hulme, who, while he has rectified many errors 

 of the analysts, has confirmed the more important and more valu- 

 able. Dr. Hulme found that light is one of the first, perhaps the 

 first elementary substance that flies off during decomposition : 

 hence it can only be obtained from putrescent fishes, or pieces of 

 fishes in a putrescent state or stage of incipient putrefaction; for 

 after putrefaction is computed, light escapes no longer in a visible 

 form, either forming new combinations with the other gasses that 

 are now escaping, or perhaps having entirely escaped already. He 

 found, also, that it was in a considerable degree adhesive, and 

 would continue attached to the surface of the body that had emit, 

 ted it, or to the finders or any other substance to which it was 

 transferred by srraping. Thus pieces of herring were observed to 

 continue lun.inous for about forty-eight, and thence to sixty hours 

 after they first discovered light, and then ceased to be luminous any 

 longer. Having scraped off the luminous body, he mixed it with 



