332 PHOSPHORESCENCE OF DECAYING ANIMAL MATTER. 
appointed for the lovers’ rendezvous,” would not seem so incor- 
rect as the ideas of poets on subjects of Natural History too 
frequently are.—Regarding the uses of the luminosity of the 
lower marine tribes, it is more difficult to form a definite 
idea; since many of them are fixed to one spot during the 
whole of life, and in many others the.sexes do not require to 
seek each other. 
402. It not unfrequently happens, that an evolution of 
light takes place from the bodies of animals soon after their 
death, but before their decomposition has advanced far. 
This has been most frequently observed to proceed from the 
bodies of Fishes, Mollusks, and other marine tribes ; but it 
has been seen also to be evolved from the surface of land 
animals, and even from the Human body. Indeed, some 
well-authenticated cases have been put on record, in which a 
considerable amount of light was given off from the faces of 
living individuals, who were near their end. All animal 
bodies contain a considerable quantity of phosphorus (§ 166) ; 
and it is by no means impossible that some peculiar compound 
of this substance may be formed, during the early stages of 
decomposition, or even before death, which may, by its slow 
combustion, give rise to the luminous appearance. It appears 
that the whole substance of the body of the Fire-flies is phos- 
phorescent ; for, according to an early historian of the West 
Indies, “many wanton wilde fellowes” rub their faces with 
the flesh of a killed fire-fly, “with purpose to meet their 
neighbours with a flaminge countenance.” 
Animal Heat. 
403. One of the conditions necessary for the performance 
of Vital action, is a certain amount of warmth ; and we have 
seen that the animals which alone are capable of retaining 
their activity in the coldest extremes of temperature, are those 
which have the power of generating heat within themselves, 
and thus of keeping-up the temperature of their bodies to a 
high standard. Those which do not possess a power of this 
kind, are either rendered completely inactive, even by a com- 
paratively moderate cold, or are altogether destroyed by it. 
Those which ordinarily do possess this power are destroyed 
even more rapidly by cold, if from any cause the production 
of heat within their bodies be interrupted ; for they are the 
