LUMINOSITY or ORGANIC BEINGS. 3fany organic beings, both vegetablet and animals, possess the property of emitting light.
In cryptogiunic plants it has been observed on the filaments of schistostega osmun dacea, one of the order of hepaticm; in rhizomorpha subterranea, belonging to the order of fungi (which is not uncommon on the walls of dark, damp mines, caverns, etc., and occasionally emits a light sufficiently clear to admit of reading ordinary print); in cer tain species of agaricus (belonging to the same order); and thelaphora ceerulea (also a fungus), to which decayed wood owes its phosphoric light.
An emission of light, chiefly in flashes, has been observed in the case of a few phanerogamic plants, among which may be mentioned the garden nasturtium and mari gold, the orange lily, and the poppy. In these instances the light has been emitted by the flowers; but cases are also recorded in which the leaves, juice, etc., of certain plants have evolved light. The emission of light from the common potato, when in a state of decomposition, is sometimes very striking. Dr. Phipsou, in his work On Phosphor escence, mentions a case in which the light thus emitted from a cellarful of these vegeta bles was so strong fl8 to lead an officer on guard at Strasburg to believe that the barracks Nvere on fire. The phosphorescence in this case is probably due to the same cause as that of decayed wood.
Before proceeding to notice the principal cases in which living animals have been observed to emit light, we shall briefly refer to the emission of light by dead animal matter. The bodies of many marine animals shine after death, but in none is the phe nomenon so vivid or continuous as in the well-known boring mollusk the pholas. The luminosity of this animal after death was known to Pliny, who said that it shone in the mouths of persons who ate it; and has been made the subject of special investigation by Reaumur, Beccaria, and others. Among other results, they found that a single pilau rendered seven ounces of milk so luminous that the faces of persons might be elistinguished by it; and that, by placing the dead animal in honey, its property of emittiug light, when plunged into warm water, lasted more than a year.
It is universally known that certain kinds of dead fish, especially mackerels and her rings, shine in the dark. From a careful study of the body of a dead stock-fish in a luminous condition, Dr. Phipson finds that the phenomenon is due to a grease which shines upon the fish, and which (as it neither contains phosphorus nor minute fungi, by which the light might have been caused) contains some peculiar organic matter, which shines in the dark like phosphorus itself.
Several cases are on record in which ordinary butcher's meat has presented the phe nomenon now under consideration, but their occurrence is so rare that we need not specially notice them. It may be observed that phosphorescent light is not unfrequently observed on the dead human body by persons who visit dissecting-rooms by night. The occasional evolution of light by living human beings will be presently referred to.
The living animals which possess the property of emitting light are extremely numerous, decided cases of phosphorescence having been frequently observed, accord ing to Dr. Phipson, "in infusoria, rhizopoda, polypes, echinoderms, annelides, medusx,
tunicata, mollusks, crustaceans, myriapodes, and insects." Following the arrangement here laid down, we shall mention a few of the organisms in which the phenomenon in question is most remarkable. Among the rhizopoda the noctiluca miliaris, a minute animal very common in the English channel, stands pre-eminent. Dr. Phipson relates that he has found it "in such prodigious numbers in the damp sand at Ostend that, on raising a handful of it, it appeared like so much molten lava." It is the chief cause of the phosphorescence of the sea which is so often observed. Among the annelides, earth worms occasionally evolve a shining light like that of iron heated to a white heat. Among the tunicata, a minute animal common in some of the tropical seas, the pyrosoma Atlantua resembles a minute cylinder of glowing phosphorus, and sometimes occurs in such numbers that the ocean appears like an enormous layer of molten lava or shining phosphorus. Among the myriapodes, certain centipedes—viz., scolopendra electrica and S. phosphorea—present a brilliant phosphoric appearance. There is reason to believe tgat the former will not shiue in the dark unless it has been previously exposed to the solar rays. Luminosity in insects occurs in certain genera of the coleoptera and hemip tera, and possibly in certain lepidoptera and orthoptera. Among the coleoptera must be especially mentioned the genus lampyris, to which the variou‘ species of glow-worms (q.v.) belong, and the genus dater, to which the fireflies (q.v.) lit long. In the hemiptera there is the genus fulgora, or lantern-flies (q.v.), sonae speeie, f which are highly luminous.
The evolution of light from animals belonging to the vertebrates is extremely rare. Bartholin, in his treatise De Luce liominum et Brutorum (1647), gives an account of an Italian lady, whom he designates as " mulier splendens," whose body.shone with phos phoric radiations when gently rubbed with dry linen; and Dr. Kane, in his last voyage to the polar regions, witnessed almost as remarkable a case of human phosphorescence.. A few cases are recorded by sir H. Marsh, prof.Donovan, and other undoubted authori ties, in which the human body, shortly before death, has presented a pale, luminous appearance.
It is very difficult to give a satisfactory explanation of the above facts. The light evolved from fungi is most probably connected with chemical action, while. that emitted in sparks and flashes from flowers is probably electrical. In some luminous animals, a phosphorescent organ, specially adapted for the production of light, has been already detected, and, as anatomical science progresses, the same will probably be found in all organisms endowed with luminous or pliovhorescent properties. For fall details on the subject of this article, the reader is referred to Dr. Phipson's work, On Phosphorescence (London, 1862).