I have mentioned these phosphorescent organs of small and smallest crustaceans because not many years ago a French naturalist, my friend Professor Giard, found that many of the sand-hoppers on the great sandy shore near Boulogne are phosphorescent. A year or two later I found them myself on the shore above tide-mark at Ouistreham (Westerham), near Caen, where they had actually been mistaken for glow-worms! It was easy at night to pick up a dozen phosphorescent sand-hoppers during a stroll of five or ten minutes on the sands. Yet I have never seen them nor heard of their being seen on the English coast, and one of the results which I hope for in mentioning them here is that some of my readers will discover them on British sands and let me know. The remarkable fact about the luminous sand-hoppers is that they have no apparatus for producing light, and, as a matter of fact, do not produce it! Their luminosity is a disease, and is due (as was shown by that much-beloved teacher and discoverer the late Professor Giard) to the infection of their blood by a bacillus. Hence it is only here and there that you see the brilliant greenish ball of light on the sand due to a phosphorescent sand-hopper. And when you pick it up you find that the poor little thing is quite feeble and unable to hop. Examine its blood under the microscope and you find it teeming with excessively minute parasitic rods like those which cause the phosphorescence of dead fish, of stale bones, and occasionally of butcher's meat. Similar bacilli may be obtained by cultivation from any sea-water, and in such abundance that a room can be lit up by a bottleful of the cultivation. Perhaps all the light-producing bacteria or bacilli are only varieties of one species—perhaps they are distinct species. Whether a species or a variety, that which gets into the blood of the sand-hopper and gives it the luminosity of a glow-worm, inevitably and rapidly causes its death—a severe price to pay for brief nocturnal effulgence. Some of the germs can be removed on a needle's point from the dead sand-hopper and introduced by the most delicate puncture into a healthy sand-hopper or into a young crab, with the result that they too become illuminated, the bacillus multiplying within them. Being thus morbidly illuminated and having astonished the crustacean, not to say the human world, by their alarming brilliance, they quickly perish: a little history which may be read as a parable. The sand-hoppers give the disease to one another. It is, of course, a merely non-significant thing that the bacillus happens to set up light vibrations. Its chemical activity is concerned with its nourishment and growth, and in the course of these processes it not only produces light but poisonous by-products which kill its host. Some day we may get an "immune" race of sand-hoppers who will acquire the illuminating bacillus and defy its poison. Then we shall have a permanent and happy breed of brilliant sand-hoppers illuminating the dark places of the seashore.
It is conceivable that some of the disease-producing bacilli (bacteria, cocci, etc.) which multiply in man's blood and tissues should also produce light vibrations, and if one could be found that would render the blood luminous, whilst not producing much pain or malaise, no doubt some excuse would be found for its use as a fashionable toilet novelty. Cases are on record of luminosity of the surface of the body and its secretions being developed during serious illness by human beings, especially in acute phthisis; but these ancient records need confirmation.
Luminous bacilli or bacteria only give out light when free oxygen is in the water or liquid inhabited by them. A chemical combination of the oxygen with substances in the bacteria is the necessary condition of their evolution of light. When frozen, these bacteria cease to be luminous—the chemical combination cannot take place when the substance of the bacterium is frozen solid and maintained in that condition; the liquid condition is a necessary condition for these changes. These luminous bacteria have been used recently by Sir James Dewar in the Faraday Laboratory of the Royal Institution (where Sir James has shown them to me), for the purpose of investigating the action of intense cold on living matter. Although their luminous response to oxygen is arrested when they are frozen, yet immediately on allowing the temperature to rise above freezing-point the response of the living matter to oxidation recommences, and a luminous glow is seen. Hence we have in this glow a ready means of answering the question, "Does extreme cold, of long duration, destroy the simplest living matter?" Sir James Dewar has exposed a film of these bacteria to the extremest degree of cold as yet obtained in the laboratory, that at which hydrogen gas is solidified, and he has kept them in this, or nearly this, degree of cold for several months. Yet immediately on "thawing" the luminous glow was visible in the dark, showing that the bacteria were still alive. Curiously enough, whilst all chemical action in living matter can be thus arrested by extreme cold, and yet resumed on rise of temperature and restoration to the liquid condition, so that the old phrase and the conception of "suspended animation" are justified—yet there is one widely-distributed form of activity, the effect of which the bacteria, even when hard frozen, cannot resist, namely, that of the blue and ultra-blue rays of light. These rays, if allowed to fall on the hardest frozen bacillus, get at its chemical structure, shake it to pieces, destroy it. Hence Sir James Dewar argues that, whilst it would appear that the extreme cold of space would not kill a minute living germ, and prevent it passing from planet to planet, or from remotest space to our earth, yet one thing which is more abundant in space than within the shell of our atmosphere is absolutely destructive to such minute particles of living matter, even when hard-frozen, and that is intense light, the ultra-visible vibrations of smallest wave-length.
A dance on the seashore: a sketch by Edward Forbes (1852).
CHAPTER XVIII
A SWISS INTERLUDE
AFTER the hot summer of 1911 I escaped from London in September and made straight for Interlaken. Thence I was "wafted" by the electric railway to the "Schynige Platte"—a wonderful hill-side, 4500 feet above the "Bödeli," the flat meadowland in which Interlaken is placed. At the Schynige Platte we are separated to the south from the Jungfrau and the great Oberland range of mountains only by a deep rift in which rushes the "Black Lütschine," coming down from Grindelwald to join its "white" brother-torrent close beneath us at Zweilütschinen. To reach the "Platte" we creep in our train up the northern side of the mountain—one of whose peaks is known by the curious name "Gummihorn"—for more than an hour without a glimpse of what is on the other side. Then, when we are 6000 feet above sea-level, we enter a short tunnel in the shoulder of the mountain, and all is dark. When the train emerges every one in it gasps. You hear a cry from every mouth—for the scene is astounding! Coming through that tunnel we have stolen surreptitiously upon a band of gigantic snow-white brethren—the Wetterhörner, the Schreckhörner, the Eiger, the Mönch, the Jungfrau, the Mittaghorn, the Breithorn, and the Tschingelhorn. There they are—lying close to us, unaware of our approach—naked and unashamed, glistening in the sunlight, variously stretched in their immense repose. One feels on seeing them thus free from every scrap of cloud and clothing as though one had intruded upon a glorious company of titanic beings innocently sunning themselves in perfect nudity. It is with the sense that humble apologies for the intrusion are due to them, and will be graciously accepted because we hold them in such profound admiration and reverence, that we venture, little by little, to let our eyes dwell on their wondrous beauty. There are moments, it must be confessed, when we feel a qualm of modesty and are unwilling to take advantage of our rare chance—moments when we should not be surprised if one of the giants were to hurl a command at us—in terms of thunder and avalanche—ordering us at once to retire to the other side of the Gummihorn and leave them to their rightful privacy. There is no great view of snow mountains at close range—not even that from the Gornergrat—which is at once so fine and so easily accessible.