672 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
investigating how far some heliotropic effects and retardations of growth 
in higher plants, and the retarding action of light on growth generally, 
are due to destructive oxidations in the cell-sap of highly combustible 
food-materials, at or just prior to the moment they are ready to be 
assimilated into the living substance of the protoplasm. 
Thermophilous Bacteria.* — Mdlle. Lydia Rabinowitsch has verified 
and extended the observations of Globig, who found that certain bacteria 
have an optimum temperature of from 50°-70°. The behaviour of these 
bacteria on different media and at different temperatures was tested, 
and an attempt made to ascertain under what meteorological conditions 
they would grow. The cultivation and isolation of bacteria on agar is 
not easy, on account of the great amount of condensation water and of 
the rapid drying. These difficulties were, however, skilfully obviated. 
Four species were isolated from earth, and these were afterwards 
demonstrated in fresh snow. Spree water contained 7000-8000 thermo- 
philous bacteria in 1 ccm. They were found in cow and horse dung, 
and in the intestinal tract of the horse, cow, goat, guinea-pig, rabbit, 
dog, mouse, pigeon, duck, parrot, man, frog, Varanus pythau. From the 
rabbit, cow, and mouse, three species were isolated. As these bacteria 
were infrequent in the stomach, frequent in the small intestine, and 
most numerous in the large intestine, the author came to the conclusion 
that they increased in the body. At higher temperatures they grew 
anaerobically, but more slowly as aerobes at lower ones ; though, con- 
versely, simultaneously made cultures always developed more quickly 
aerobically at higher, than anaerobically at lower temperatures. Thermo- 
philous bacteria are found on wheat, oats, and barley. In barley they 
are most numerous during the middle stage of germination. The author 
considers it not improbable that thermophilous bacteria have some share 
in the spontaneous heating of malt, manure, wool, hay, and tobacco. 
Fluorescing Bacteria. f — Herr K. Thumm has made experiments with 
Bacillus jiuorescens tenuis , Bac. fl. putidus, Bac. fl. albus , Bac. enythro- 
sporus , Bac. viridans, Bac. pyocyaneus, Bac. syncyaneum , for the purpose 
of ascertaining whether the pigment produced was alike in all cases, 
whether the production is dependent on the development of the organism, 
or whether it is influenced by the nutritive medium. The experiments 
were numerous, and only some of the more important results can be 
referred to. All fluorescing bacteria, when cultivated in alkaline media, 
produced first a blue fluorescence, which afterwards becomes of a green 
hue, while the substratum assumes a yellow colour. All the species 
form alkali and the same pigment. If acid-forming bacteria also be 
present in a culture, they prevent the fluorescence. All oxidise grape 
sugar to acid, which is neutralised by the ammonia afterwards formed. 
The formation of pigment and ammonia takes place only in the presence 
of oxygen. 
Fluorescing Function of Microbes.^ — According to M. C. Lepierre, 
fluorescence is due to an extremely complex function, and up to a certain 
* Zeitschr. f. Hygiene u. Infekt., xx. No. 1, p. 154. See Centralbl. f. Bakteriol. 
u. Parasitenk., 2 te Abt., i. (1895) pp. 585-6. Cf. this Journal, ante, p. 346. 
t Arb. a. d. Bakter. Inst. d. Techn, Hochschule zu Karlsruhe, i. (1895) p. 291. 
See Centralbl. f. Bakteriol. u. Parasitenk., 2 te Abt., i. (1895) pp. 586-8. 
t Ann. Inst. Pasteur, ix. (1895) pp. 643-63. 
