890 SPECIAL PHYSIOLOGY. 



Dead animal matter is frequently luminous or phosphorescent. The 

 surfaces of the muscles and other soft parts of bodies undergoing dis- 

 section in anatomical schools have sometimes been seen to emit a 

 brilliant light; and luminous exhalations from graveyards, especially 

 from the recently exposed soil, have not unfrequently been observed. 

 The remains of decaying animal matter generally, may also become 

 phosphorescent; but this more particularly happens in the case of 

 marine Fishes and the marine Mollusca, Crustacea, and Coelenterata. 

 This is also at present attributed to a true phosphorescence, some im- 

 perfectly oxidized phosphuretted compound being supposed to be the 

 result of an incipient stage of decomposition. It disappears on the 

 occurrence of actual putrefaction. 



The warm-blooded Yertebrata apparently possess even less power than Man, 

 of evolving light from the living body, or authentic cases of such an event would 

 have been recorded. The light seen in the eyes of the cat and other creatures 

 in the dark, is merely a reflection from the iridescent portion of the choroid 

 coat within the eyeball. Amongst the cold-blooded Yertebrata, the gray liz- 

 ard is said to deposit eggs which are sometimes luminous ; and a species of 

 frog in Surinam, is described as emitting light, especially from the mouth. 

 Certain cases of luminosity amongst marine Fishes, may be owing to the agi- 

 tation and percussion of smaller luminous animals in the water ; but a marine 

 species of Scopelus, allied to the Salmonida, is said to emit stars of light from 

 the body and head ; it is in one of these fishes that Leuckart has recently de- 

 scribed scattered organs, containing lens-like bodies, which are regarded by 

 him as eyes (p. 477). These may be light-reflecting organs. 



The most remarkable and characteristic examples of the emission of light 

 from the living animal body, occur amongst the Non-vertebrate creatures. 

 Some of these are met with in air-breathing animals. Thus amongst the A.n- 

 nulosa, two families of Coleopterous insects or beetles, viz., the Elaterida and 

 Lampyrida, furnish us with the well-known examples of the fire-flies and 

 glow-worms. The fire-flies proper to hot climates, give out a very brilliant 

 light from two spots, one on each side of the thorax, and from a third, on the 

 under side of the same part ; the light is present in both sexes. In the glow- 

 worms, however, the light is softer, and though observed in the male, and, 

 even more feebly, in the chrysalis, in the larvae, and in the egg, it is decidedly 

 more striking in the female ; it is also chiefly observed at particular seasons. 

 It proceeds from the under side of the three last segments of the abdomen. 

 Examined under high magnifying powers, the luminous patches are seen to 

 consist of little sacs, containing a yellowish granular matter, which is the lu- 

 minous substance. These sacs are closed by horny lids, having peculiar flat 

 surfaces, suited to the diffusion of the light ; the granular matter and sacs 

 are traversed by numerous air-tubes, or tracheae. The light is given out, even 

 after the segments are removed from the rest of the body, and luminous 

 streaks may be produced by rubbing the yellow matter between the fingers. 

 There seems no doubt that the cause of the luminosity, is the feeble combus- 

 tion of some organic compound excreted by the animal. It is said, however, 

 not to contain phosphorus in any appreciable quantity, and the product of its 

 combustion is carbonic acid. (Matteucci.) Other alleged instances of lumin- 

 ous winged Insects are doubtful. Amongst the Annulosa, some Centipedes, 

 and, under certain circumstances, the common earth-worm, also present ex- 

 amples of luminosity. Amongst the Mollusca, there are luminous air-breath- 

 ing Gasteropoda. 



By far the larger number of luminous Non-vertebrate animals, is found 

 amongst the aquatic breathers, and exclusively, perhaps, amongst the marine 

 species. Of the Molluscous marine animals, the Cephalodopous Octopus, the 

 Pteropodous Cleodora, and the Lamellibranchiate Pholas, exhibit luminosity. 

 Many Molluscoid animals, but especially the Tunicated Salpida and Pyroso- 

 mida, are eminently distinguished for this property. Again, many minute 



