ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 
81 
then, having been cooled down to 40°, is inoculated with somo kind of 
bacterium ( B . typhosus , B. coli comm., B. pyocyancus , B. choleras, &c.). 
The bacteria arc to be regularly disseminated throughout the media, 
and then the agar is poured into a flat glass vessel. When cold and set, 
some dovice — e. g. a cross or letters of black paper — is fixed on the 
under surface of the capsule. The capsule is turned upside down, and 
the under surface of the agar plate exposed for 1-1^ hours to direct, or 
5 hours to diffuse sunlight. The plate is then placed in a dark place, 
and in 24 hours the device appears from the development of the colonies, 
the rest of the plate being a blank. An illustration taken from a photo- 
graph of an agar plate sown with typhoid bacteria shows the result of 
the action of light extremely well. 
Effect of Chloroform on Bacteria.* — M. Kirchner obtained the 
following results from his experiments with chloroform on bacteria : — 
(1) Chloroform possesses no inconsiderable power over a largo 
number of bacteria, but not over the spores of most of them. Of the 
pathogenic bacteria, anthrax, cholera, and typhoid bacilli, and St. pyo- 
genes aureus were quickly devitalized, while the spores of tetanus and 
anthrax were unaffected even after prolonged action. 
(2) Chloroform has no inhibitory action on spore development; for 
at a suitable temperature, and in the presence of chloroform, the spores 
become bacteria, and then the action of chloroform takes effect. 
(3) Chloroform is no disinfectant in the broader sense of the word, 
but it possesses a certain antiseptic value which renders it suitable for 
preserving albuminous substances, as it represses fermentation and 
putrefaction. 
(4) To be efficient, chloroform must be used not only in the undis- 
solved condition, but in saturated solution, care being taken to prevent 
evaporation. 
Soluble Pigments produced by Bacteria, f — M. L. Viron has suc- 
ceeded in isolating some soluble pigments produced by bacteria, and in 
cultivating the micro-organisms which made them. 
From an orange-flower water was obtained, by evaporation, a 
substance consisting of greenish granules, of rodlets and yellowish 
scales. This organic residue was composed of three different pigments, 
imparting to solutions violet, green, and yellow colours. As these 
pigments were not developed in sterilized water, they must have been 
due to the presence of living organisms, and by means of plate cultiva- 
tions on different media some chromogenic cultures were isolated. The 
pigment was produced only on solid media. One of these organisms is 
regarded as a variety of M. cyaneus Schroter ; another is called Bacillus 
aurantii , largish rodlets grouped in pairs ; and a third B. fluorescens 
liquefaciens. Injection of the coloured fluid produced by this last 
showed pathogenic properties, but with the two first it was not so. 
After being bred through a few generations, these micro-organisms lost 
the power of producing pigment, but it came back again if they were 
cultivated in stronger nutrient media. 
* Zeitschr. f. Hygiene, viii. (1890) pp. 465-88. See Bot. Centralbl., 1. (1892) 
pp. 359-60. f Comptes Rendus, cxiv. (1892) pp. 179-181. 
1893. G 
