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Habana. The enforcement of the measures began April 20, 1903. The mortality which before had averaged 150 deaths a month fell to s in the month of April and to 4 in June. In January, 1904, there were recorded only 3 deaths.

France decided to follow these encouraging examples. The governor-general of French Western Africa, M. Roume, adopted an administration analogous to that of Habana and Rio de Janeiro, and he knew how to profit by these examples. The result was not long delayed. On May 29, 1905, an imported yellow-fever patient died in Dakar. Thanks to the precautions taken, this death has not been followed by a single other one. The threatened epidemic was stopped at its first stride and that colony saved from a new disaster such as it had suffered twice in less than thirty years.

LUMINOSITY IN PLANTS.

By Prof. Dr. Hans MOLISCH.

Sixty-two years ago, at the twenty-first meeting of German scientists and physicians at Gratz, over which no less a personage than the famous chemist, J. von Liebig, presided, an Austrian investigator, J. T. Heller, gave an address upon the luminosity of decaying wood, and advanced the idea that the production of light did not come from the decaying wood itself, but from a fungus which penetrated the wood. Not long after this the same investigator carried out a thorough examination of light coming from decaying animals and plants, and discovered that the luminosity in the flesh of dead marine animals and various decaying plant substances was not a purely chemical but a biological process, uniformly produced by a certain plant, a fungus. That is to say, it is not the flesh of a fish or the wood that is luminous, but a fungus living upon these and penetrating them in proportion to their decay. It may be noted that priority for this discovery has been accorded, though unjustly, to the gifted physiologist, E. Pflüger, because Heller's investigations dropped entirely out of sight, and were only recently discovered by me. The priority unquestionably belongs to Heller.

By understanding that the problem is a biological one, an important basis has been gained for further investigations. As, furthermore, R. Koch has enriched scientific knowledge by his bacteriological technique and the method of pure cultures of bacteria, the cultivation of various light-producing bacteria and recently also of luminous fungi has been successfully undertaken. We are now in condition to approach the subject of distinguishing between various species, of investigating the conditions for luminosity, the nature of the light, and the problem of light development. If we exclude light development in the Peridinem, which are sometimes referred to the animal and sometimes to the vegetable kingdom and which play an important part in the striking spectacle of marine phosphorescence; and if we ignore the so-called glimmer of flowers, first observed by the daughter of Linnæus, which is attributable to an entirely different cause, probably a purely physical one, and most likely to the appearance of St. Elmo's fire, all light-producing plants may be said to belong to the Fungi; that is, to the Bacteria and the mycelial Fungi.

a Translation of Die Lichtenwickelung in den Pfanzen, von Prof. Dr. Hans Molisch, Leipzig, 1905.

In order to avoid misunderstanding it may be said that in speaking of light-producing plants I refer invariably to those plants which of themselves produce the light, their own and not reflected light, to which latter phenomenon are to be referred the wonderful iridescence of many sea algx, the remarkable emerald green gleam of the luminous moss Schistostega osmundacea, and the reflection, like liquid gold, of the Flagellate, Chromophyton rosanofii. There are in round numbers thirty different kinds of bacteria and about half as many other fungi which have the power of luminosity. If we compare this to the combined number of existing plant species they doubtless appear as a very small proportion. Nevertheless we are frequently surrounded with luminous objects in nature and even in the household, because certain ones of these light-producing fungi are among the most common of all plants. Of these I will give a couple of examples.

Until recently luminosity in butchers' meat was considered to be a spectacle of rare occurrence, a curiosity the cause of which was unknown and the conditions producing it infrequent. When I undertook an investigation of the matter I lacked proper material; and although I communicated with various people and institutions where luminous meat would be most likely to be found, not a single specimen was supplied to me for fully two years. I was about ready to abandon the undertaking when the idea came to me to examine meat supplied to me for household use, and to my astonishment it appeared that such meat, kept for from one to three days in a cool place, began in many instances to spontaneously produce light. In following up the matter I found that the luminosity much more frequently occurred if ordinary butchers' meat was so immersed in a 3 per cent solution of salt that about one-half of it remained out of the liquid. Experiments with meat carried on for three months afforded not less than 87 per cent of cases of luminosity; thus, experiments with beef afforded 89 per cent, experiments with horseflesh 65 per cent. By means pure cultures it was demonstrated that the cause of the luminosity was invariably the same intensely luminous bacterium, namely, Bacterium phosphoreum (Cohn) Molisch. As I have carried on similar researches for a number of years, not only in the city of Prague but in other cities as well and with essentially the same results, it can be stated that the spontaneous luminosity of meat is in fact a quite common occurrence.

The cause of this light development, Bacterium phosphoreum, is one of the most widely distributed of the bacteria. It is found on meat in refrigerators, in slaughterhouses, in butcher shops; in fact, it finds an entrance into our kitchens where meat is usually prepared. For in no other way can we explain the fact that so many specimens of meat display the power of spontaneous luminosity. I have of late come upon another form of light production, which, although of common occurrence, is practically unknown. I refer to light from decaying leaves. During walks taken at night in the Tropics, especially in Java, I frequently found the dead leaves of Bambusa, Nephelium, Aglaia, and other plants to be luminous in the darkness. On returning to Europe with the experiences gathered in the Tropics, I looked into the same subject on native ground and found that luminous dead leaves of the oak and beech are quite common in middle Europe. The leaves must be in a somewhat moist condition and to some extent decayed. Such leaves, especially, as display on account of decay a somewhat yellowish or ashen color or show spots of yellow and brown give a particularly beautiful light. The luminosity is usually local, rarely over the entire surface—a white, soft, steady light. Here also the luminous cause is not the leaf substance, but the living fungus within it.

According to my own observations, no inconsiderable percentage of fallen oak and beech leaves are luminous in the summer time; and on all sides the floor of the forest is illuminated with light, feeble, indeed, but easily detected. Unfortunately I have not as yet been able to isolate the fungus which produces this light of decaying foliage. Still I have employed with advantage the methods of pure cultures with the fungus, producing light in wood, and thereby have recognized in Agaricus melleus and Mycelium v the two fungi which with us most frequently cause this luminosity. At the same time it has become evident that certain cryptogams generally considered as luminous fungi, such as Xylaria Hypoxylon, must be stricken out of the list of the Photomycetes, and to this may also be added Trametes pini.

In Bacterium phosphoreum (Cohn), Molisch and Mycelium (necessarily so called at present, as despite years of cultivation it has not yet fruited), are secured two remarkably valuable experimental adjuncts for accurately studying light development in a definite way, because of their relatively powerful intensity of light and the unusually long period that they are luminous.

Luminosity and the growth of luminous bacteria are dependent, among other things, upon certain salts and organic substances. Table salt plays a prominent part in this respect, seeing that as a rule these bacteria are marine, and for this reason 3 per cent of table salt is generally added to the culture medium. The salt does not serve as

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food, but rather performs an osmotic function, by rendering the culture medium more or less isosmotic to the cell contents of the bacteria. Other salts can in the same way replace table salt, as potassium chloride, magnesium chloride, calcium chloride, potassium nitrate, potassium iodide, and potassium sulphate. In fact, I have the impression that potassium nitrate is more active in causing luminosity than the chlorides, such as sodium and potassium chlorides.

We are indebted to Beijerinck for some exhaustive and valuable investigations upon the relations existing between nutriment, luminosity, and growth. The method of his investigations is essentially the spreading upon thin glass plates of gelatin containing photobacteria and supplied with an excess of nutriment. When it is spread out as a thin film the bacterial field quickly becomes luminous. As soon, however, as the excess of nutriment is consumed, the light

If now we add to the gelatin a substance the influence of which on luminosity and growth we desire to test, it dissolves and is disseminated in a circle in all directions. If this added substance is a nutritive one for luminosity, we see, frequently in a few seconds, the area that was affected growing luminous. By this method bacterial fields exhibit reactions of astounding delicacy. Certain materials, preeminently lebulose and glucose, cause the field to grow luminous in a fey seconds. In this respect the photobacteria react with so minute a quantity of material that Beijerinck saw in these reactions an analogy to the Bunsen-flame reaction. In one sense this bacterial reaction is superior, in that it continues longer.

The luminous bacteria act in various ways with materials containing carbon and nitrogen. One class, called by Beijerinck Peptonbacteria, finds the necessities for growth and light development supplied in pepton or some albuminous material; the other class, called by him Pepton-carbon-bacteria, requires at the same time the presence of material containing pepton to supply the necessary oxygen and also carbonaceous matter, which is not necessarily free from nitrogen.

If the nutritive material is well adapted to both growth and a multiplication of bacteria, it will cause not only luminous fields, but fields of growth called “auxanogrammes," characterized by the innumerable colonies of bacteria that develop far more rapidly in the field where the material has been diffused than outside of it. Beijerinck calls such nutritive material “plastic.” Luminous substances are uniformly plastic though the reverse of this is not recessarily true. From this the important fact follows that light development by the luminous bacteria is not necessarily connected with either growth or respiration,

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