FOOT — ON ANIMAL LUMINOSITY. 4 7 



is present in such cases, because it is known that that process follows 

 so closely upon the heels of life, that it is present and at work upon 

 dead matter long before its presence is betrayed by those offensive pro- 

 ducts by which persons generally measure the progress of decay. 



The evolution of light has been observed in cases where local de- 

 composition was in operation upon the yet living body.* Quoy and 

 Gannaid observed phosphorescence from the ulcerated back of a living 

 turtle, from which the shell had been removed ; several luminous points 

 were plainly visible at night. It will be remembered that the cara- 

 pace is often removed from these animals, for the sake of the tortoise- 

 shell its outer layers yield, by the cruel process of lighting afire on the 

 reptile's back, the heat of which causes the plates of the dorsal shield 

 to curl upwards, and separate more readily than they do in the ordinary 

 process with a knife ; they then return the animal to the sea, on the 

 hopes that on some future occasion, when the shell has grown again, 

 they may rob it a second time. A parallel instance of the phosphores- 

 cence of a part in which disintegration of tissue was taking place in 

 the living human subject came under the notice of Dr. Stokes, and it 

 is such a remarkable observation that I shall take the liberty of quot- 

 ing it in his own words : — " When I was residing in the Old Meath 

 Hospital, a poor woman, labouring under an enormous cancer of the 

 breast, was admitted. The breast was much enlarged, and presented a 

 vast ulcer with irregular and everted edges, from all parts of which a 

 quantity of luminous fluid was constantly poured out. Upon being 

 asked whether she suffered much pain, she answered, 'not now, Sir, 

 but I cannot sleep, watching this sore, which is on fire every night.' 

 I directed that she should send for me whenever she perceived the 

 luminous appearance, and on that night I was summoned between ten 

 and eleven o'clock, the lights in the ward having been then ex- 

 tinguished ; she was sitting leaning forward, the left hand sup- 

 porting the tumour, while with the right she every now and then 

 lifted up the coverings of the ulcer to gaze on this, to her, supernatural 

 appearance. The whole of the base and edges of the cavity phospho- 

 resced in the strongest manner. The light was steady. I directed 

 that the ulcer should remain open, while I retreated gradually, keeping 

 my eyes fixed on the light, which I found distinctly visible at the end 

 of the ward, which must have been more than twenty feet from her 

 bed. The light within a few inches of the ulcer was sufficient to enable 

 me to distinguish the figures on a watch dial. I have no very distinct 

 recollection of the colour of the light, but I remember that its intensity 

 was variable, it being on some nights much stronger than others. "j- 



Coming to the subject of luminosity in living and healthy ani- 

 mals — to what may be called Physiological Phosphorescence — it will be 

 found that this kind of phosphorescence is principally, but by no 



* " An. d. Sci. Nat.," 1825, t. iv., p. 8, note. 



f Sir H. Marsh's " Essay on Evol. of Light,"' op. cit., p. 54. 



