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B A C T E R I O L O G Y 59 teria grow but do not phosphoresce. If we now streak 100° C. and upwards, can be killed by exposure to rays of these plates with an organism, e.g., a yeast, which sac- reflected light at temperatures far below anything injuricharifies starch, it is possible to tell whether maltose or ous, or even favourable to growth. He also showed that levulose and fructose are formed; if the former, only the bactericidal action takes place in the absence of food those plates containing P. phosphorescens will become materials, thus proving that it is not merely a poisoning luminous; if the latter, only those containing P. Pflugeri. effect of the altered medium. The principal experiments It has long been known that the production of vinegar also indicate that it is the rays of highest refrangibility depends on the oxidization of the alcohol in wine or beer - the blue-violet and ultra-violet rays of the spectrum— to acetic acid, the chemical process being prob- which bring about the destruction of the organisms (Figs. bacten'af carried out in two stages, viz., the oxida- t, 8). The. practical effect of the bactericidal action of tion of the alcohol leading to the formation of solar-light is the destruction of enormous quantities of aldehyde and water, and the further oxidation of the germs in rivers, the atmosphere, and other exposed situaaldehyde to acetic acid. The process may even go farther, tions, and experiments have shown that it is especially the and the acetic acid be oxidized to«C02 and OH2; the art pathogenic bacteria—anthrax, typhoid, <fcc.—which thus of the vinegar-maker is directed to preventing the accom- succumb, to light-action .; the discovery that the electric arc plishment of the last stage. These oxidations are brought is very rich in bactericidal rays led to the hope that it about by the vital activity of several bacteria, of which could be used for disinfecting purposes in hospitals, but four—Bacterium aceti, B. pasteurianum, B. kiitzingianum, mechanical difficulties intervene. The recent application and B. xylinum—have been thoroughly studied by Hansen of the action of bactericidal rays to the cure of lupus is, and A. Brown. It is these bacteria which form the zoo- however, an extension of the same discovery. Even when glcea of the “mother of vinegar,” though this film may the light is not sufficiently intense, or the exposure is contain other organisms as well. The idea that this film too short to kill the spores, the experiments show that of bacteria oxidizes the alcohol beneath by merely con- attenuation of virulence may result, a point of extreme densing atmospheric oxygen in its interstices, after the importance in connexion with the lighting and ventilation manner of spongy platinum, has long been given up; but of dwellings, the purification of rivers and streams, and the explanation of the action as an incomplete combustion, the general diminution of epidemics in nature. depending on the peculiar respiration of these organisms— . As we have seen, thermophilous bacteria can grow at much as in the case of nitrifying and sulphur bacteria— high temperatures,, and it has long been known that some is not clear, though the discovery that the acetic bacteria forms develop on ice. The somewhat different will not only oxidize alcohol to acetic acid, but further question of the resistance of ripe spores or cells Bacteria oxidize the latter to C02 and OH2 supports the view that to extremes of heat and cold has received atten- W beat' the alcohol is absorbed by the organism and employed as tion. Kavenel, Macfadyen, and Rowland have shown that its respirable substance. Promise of more light on these several bacilli will bear exposure for seven days to the oxidation fermentations is afforded by the recent discovery temperature of liquid air (-192° C. to -183° C.) and that not only bacteria and fungi, but even the living cells again grow when put into normal conditions. More of higher plants, contain peculiar enzymes which possess recent experiments have shown that even ten hours’ the remarkable property of “ carrying ” oxygen—much as exposure to the temperature of liquid hydrogen - 252° C. it is carried in the sulphuric acid chamber—and which (21° on the absolute scale) failed to kill them. Farmer have therefore been termed oxydases. It is apparently has shown the probability that in all these cases of the presence of these oxydases which causes certain wines resistance of seeds, spores, &c., the fact that completely to change colour and alter in taste when poured from dry albumin does not lose its coagulability on heating to bottle to glass, and so exposed to air. 110° C. for some hours may be of importance, since it is Much as the decade from 1880-90 abounded with well known that completely ripe spores and dry heat are investigations on the reactions of bacteria to heat, so the conditions of extreme experiments. No sharp line can be drawn between pathogenic and Bacteri cov ries ^°^0W^nS decade was remarkable for disand light. p regarding the effects of other forms of non-pathogenic Schizomycetes, and some of the most radiant energy. The observations of Downes marked steps in the progress of our modern and Blunt in 1877 left it uncertain whether the bacteri- knowledge of these organisms depend on the Path°s:enic cidal effects in broth cultures exposed to solar rays were discovery that their pathogenicity or virulence acter!a' can be modified—diminished or increased—by definite treatment, and, in the natural course of epidemics, by alterations in the environment. Similarly we are unable to divide Schizomycetes sharply into parasites and saprophytes, since it is well proved that a number of species— facultative parasites—-can become one or the other according to circumstances. These facts, and the further knowledge that many bacteria never observed as parasites, or as pathogenic forms, produce toxins or poisons as the result of their decompositions and fermentations of organic substances, have led to important results in the applicaPio. 9. Ginger-beer plant, showing yeast (Soccharomyces pyriformis) entangled tions of bacteriology to medicine. Bacterial diseases in the higher plants have been m the meshes of the bacterium (B. vermiforme). (Original.) described, but the subject requires careful treatment, due to thermal action or not. Further investigations, in since several points suggest doubts as to the which Arloing, Buchner, Chmelewski, and others took organism described being the cause of the ®ac*e£/os/s part, have led to the proof that rays of light alone are disease referred to their agency. Until recently n P ants‘ quite ^ capable of killing these organisms. The principal it was urged that the acid contents of plants explained questions were satisfactorily settled by Marshall Ward’s their immunity from bacterial diseases, but it is now experiments in 1892-93, when he showed that even the known that many bacteria can flourish in acid media. spores of B. anthracis, which withstand temperatures of Another objection was that even if bacteria obtained