ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1009 



organisms a micrococcus of globular form (^Micrococcus cereus) was dis- 

 covered ; this was found to be a very efficacious nitrifying agent. The 

 authors quote experiments to prove that for the process of nitrification the 

 presence of bacteria is not absolutely essential. It is further shown that 

 among the organisms which liquefy nutritive gelatin Bacillus saprogenus, 

 B. fluidificans, and Micrococcus luteus, when thrown on to sand in cultivating 

 liquids, not only do not produce nitrates, but even destroy them comj)lotely ; 

 on the other hand, these same organisms, taken from jiotato-cultures, 

 far from destroying the nitrates, are among the most active agents in 

 producing them. 



New (Indigogenous) Microbe.* — M. E. Alvarez reminds us that the 

 indigo of commerce is obtained by the maceration of the leaves of Indigo- 

 fera, which contains a glucoside which is soluble in water ; the solution 

 is allowed to be exposed to the air. He finds from the experiments he 

 has made, that indigo is a fermentation-product, and that this fermentation 

 is caused by a special microbe, which is rod-shaped and much resembles 

 the microbes of pneumonia and rhinoscleroma. These latter also produce 

 the indigo-fermentation, while the indigogenous bacterium has pathogenetic 

 properties, causing either a temporary local inflammation, or death with 

 congestions and fibrous exudations ; the parts especially affected are the 

 genito-urinary organs. 



Certain Properties of Phosphorescent Bacteria.f — Prof. J. Forster, in 

 conjunction with Dr. C. B. Tilanus, has made pure cultivations of bacteria 

 which produce phosphorescence, and found that these micro-organisms have 

 special properties. 



By Koch's plate method those bacteria which under the Microscope 

 appear as short thick rods, are easily cultivated if the gelatin contains 

 2-3 per cent, of salt. Bacteria obtained pure (bacilli) which do not liquefy 

 gelatin, live and multiply in neutral or slightly alkaline nutritive media, 

 even if very dilute, provided the necessary quantity of salt be present. 

 In a gelatin made from fish they grew well with 6 per cent, of salt, while 

 7 per cent, decreased, and a still higher percentage altogether stopped their 

 multiplication. On the other hand, an admixture with distilled water soon 

 killed the bacilli, so that a weak salt solution was compulsory when a 

 gelatin culture was placed on a cover-glass. 



Pure cultivations of these bacteria, so long as atmospheric air is present, 

 emit light in proportion to the size and age of the colonies, so that a plate- 

 cultivation looks like the sky on a starry night. Plate or tube cultivations 

 may be photographed in a perfectly dark room and a very clear picture 

 obtained of the colonies. Although the light emitted even from large 

 colonies is not strong, it is strong enough to suffice for a microspectro- 

 metric examination. Observed in the dark with the Zeiss- Abbe micro- 

 spectrum ocular and 3 Leitz upper lens with a slit 1/3 mm., it was seen 

 that a colony 1 mm. in diameter gave an apparently continuous spectrum 

 between A 0-58-0 -43, the brightness of which was greatest between 

 0" 48-0 -51, and diminishing more quickly towards the red end than 

 towards the violet. The spectrum of a weak galvanic incandescent light 

 of about the same intensity was brightest at A • 60, while at 0-50 no light 

 was perceptible, so that the slight extension of the bacterial spectrum 

 towards red and violet is dependent on the feebleness of the light of the 

 spectrum. Colour differences in the spectrum are not recognizable, and 



* Comptes Rendus, cv. (1887) pp. 286-9. 



t Centralbl. f. Bactoriol. u. Parasitenk., ii. (1887) pp. 337-40. 



