ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
537 
inoculated with a drop of anthrax blood, and incubated at 30°-33° for 
8-10 days. In the tubes containing the most carbolized bouillon there 
was no growth and the bacteria were dead, while in the least carbolized 
there was not only growth but spore-formation. 
In a number of tubes containing an intermediate quantity of carbolic 
acid, sporeless bacteria developed. If these last were cultivated, growth 
was free enough, but no spores ever developed even under the most 
favourable conditions. 
When it is remembered that numerous bacteria have shown both 
physiological and morphological aberrations, such as alterations in 
virulence, in pigment formation, &c., in the size and arrangement of the 
cells, the foregoing phenomena seem to indicate that changes in the 
environment of bacteria may endow them with characters, morphological 
and physiological, differing from those of the standard by which they 
are recognized. 
Bacillus cyanogenes, the Microbe of Blue Milk.* — M. 0. Gessard 
propounded to himself the question whether the pigment produced by 
B. cyanogenes was one or various, and made an investigation into the 
conditions under which pigment was produced. He found that under 
natural conditions the blueness of milk is developed in association with 
an acid reaction of the medium, and is observed as blue bands or flakes. 
The addition of alkalies turns the pigment red, but on treatment with 
acids the blue colour returns. The author used a cultivation of the 
microbe obtained from Hueppe’s laboratory. When this was bred in 
bouillon a fluorescing pigment was produced, and with egg-albumen an even 
better result was obtained. The addition of a few drops of acetic acid 
caused the fluorescence to disappear and a bluish hue to develope. This, 
the pigment of blue milk, is distinguishable from that of B. pyocyaneus 
in not being soluble in chloroform. It would seem that both pigments 
were formed in the same cultivation, and the author succeeded in breed- 
ing three different varieties, one of which produced blue pigment, the 
second a green fluorescing pigment, while the third was colourless. 
The blue pigment is produced only when the medium is acid, and 
the author allowed B. cyanogenes to form the acid by cultivating in milk 
or bouillon, to which 2 per cent, glucose had been added, a beautiful 
blue being the result. 
Lactic acid would seem to be the chief exciting influence of the 
production of the blue colour ; for example, in the solution composed of 
ammonium lactate 1 per cent., neutral phosphate of potash 0*5 per cent., 
and magnesium sulphate 0‘ 25 per cent., a fine blue colour is produced, 
while if the ammonium lactate be replaced by ammonium salts of other 
organic acids, only bluish or grey tones are produced. Succinic acid 
may, however, replace lactic acid, a result explained by the similarity 
of their constitution. In itself milk does not possess any special 
property for the formation of blue pigment, this being due to the lactic 
fermentation taking place therein. If this fermentation do not occur, no 
pigment is produced ; for the mere addition of sodium lactate only 
produces a green pigment, and the addition of glucose, whereby an acid 
* Atm. Inst. Pasteur, v. (1891) pp. 737-57. See Centralbl. f. Bukteriol. u. 
Parasitenk., xi. (1892) pp. 375-6. 
