(L. 3.) Light Accompanying Vital Action

Vital Secretory Phosphorescence

Under secretory phosphorescence I include all cases where animal luminosity appears due to the secretion by the animal of a substance capable of emitting light, presumably (though not certainly) due to slow oxidation. The glow-worm (Lampyris noctiluca) and the firefly (Elater noctilucus) are the stock examples of this. It is an interesting but uncertain question how far the light of these and other luminous animals is under their own control. Professor Herdman, F.R.S., kindly writing to me on the subject of animal luminosity, says:- "In many cases there is probably a connection with the nervous system (e.g., Nyctiphanes and other Schizopoda), and the luminosity is the result of a reflex, if not of a voluntary action; and so possibly might be regarded as a direct transmutation of nerve energy into an ethereal disturbance visible as light".

In many species, however, the luminous substance retains luminosity after the death of the animal.

Excretory Phosphorescence

Under this term I include the various forms of elimination of phosphorescent matter, as a waste product from the system. This last phenomenon, as will be seen, is of much importance for our present purpose. It is at present the only unquestioned form of emission of light from the human subject. It is well known that in phthisis, cancer, and other diseases where much phosphorus has been administered by the mouth, the breath, the perspiration, and other excretions and secretions, are frequently observed to be slightly luminous. The perspiration in subjects of miliaria is also said to be sometimes luminous, although the phosphorus thus excreted must come from the ordinary stock contained in the body.1

Vital Luminescence

Some experiments cited by Dr. T. L. Phipson, whose little work on Phosphorescence (1870) is still the best collection known to me of the rarer phenomena, suggest to him that the light emitted by a mushroom (Agaricus olearius), and perhaps that emitted by a centipede (Scolopendra Electrica), and a firefly (Lampyris italica), may be a luminescent phenomenon, and depend at least partially on previous absorption of light. There seems no a priori reason against this view, which, if proved true for these organisms, would probably apply to others as well.

Vital Fulguration

Certain phanerogamous plants have occasionally been seen to emit positive flashes of light. The daughter of Linnaeus had the good fortune to make the first and classical observation on the garden nasturtium in 1762, and the phenomenon has since been witnessed in sunflowers, marigolds, and orange lilies by other observers. This light appears to be truly electric, and not to be merely the result of a current passing through the organism (as when a man lights the gas with his fingers), but to imply a generation of electricity within the organism itself.

The diffused electric luminosity, which has sometimes been seen (as by Dr. Kane, the explorer, cited by Phipson, p. 161) to illuminate the human skin, may be in some sense a vital phenomenon, or may be due to friction; but in any case belongs rather to the surface of the skin itself than to the vital processes going on underneath.

1 See (for instance) Diseases of the Skin, by Dr. H. Radcliffe Crocker (1888), p. 160, etc.

Vital Photogeny

By this name I designate the direct production of light by living organisms, as a result or bye-product of their own metabolism. Such, I cannot but think, is the explanation of the widespread luminosity of low marine forms, especially when transparent:- a source of light, in comparison with which the greasy organs of glow-worm and firefly sink into insignificance. Noctiluca miliaris, to take one species alone, "offers," in the lofty language of Humboldt, "the magnificent spectacle of a starry firmament reflected in the sea." On these primitive forms Professor Herdman writes: "It is in these cases of simple, undifferentiated protoplasm that I fancy the luminosity might be an exaggeration of some necessary accompaniment of metabolism, or practically of life, i.e. of the functions of the living protoplasm. It would then be a katabolic action or molecular disturbance which might be supposed to affect the surrounding ether so as to produce light. We might imagine that this kata-bolic action goes on always in living protoplasm, but so slightly as not to produce visible light, while in some cases (cells, tissues, or organisms) it has become emphasised, and then 'seized upon' by natural selection as serving some useful purpose (which may be a very different purpose in different cases), and so perfected." "This," adds Professor Herdman, "is speculation," and it is only as such that I venture to print it here.

As will be presently seen, it is precisely the conclusion to which observations of a very different kind had already pointed me.

A few words only need be added here as to subjective or phantasmal luminosity. The immediate link between objective and subjective light may be said to be the intra-cerebral flash, seen when the optic nerve is pressed or cut, or the brain concussed.

Then come the whole series of illuminated phantasms; either simply phantasmal lights, diffused or definite, or figures seen in darkness, or otherwise more highly illuminated than the objects around them. All these sensations of light, like other phantasms, are prima facie subjective; but as with other phantasms, we have the difficulty of collective hallucinations, and the gradual merging of these phantasms into the physical phenomena with which I am here dealing.

Turning back to the luminous phenomena recorded in Mr. Moses' seances, have we now any clue as to the mechanism of their production, or as to the headings in our scheme of luminosities under which they most fitly fall? I will at once say, that at least two of the less familiar of these headings do appear to me to be applicable to lights produced under spirit control. I mean Excretory Phosphorescence and Vital Photogeny.