OXYGEN FROM COLOURED BACTERIA. 133 
weeks an active evolution of oxygen; in Sarcina aurantiaca and 
Micrococcus agilis becoming weak in 2-3 hours and ceasing in 
3-4 hours; in Bacillus brunneus becoming weak in 5-6 hours 
and ceasing in 8-10 hours. The colour of the cultures of 
B. brunneus is slightly faded on the outer surface only, in the 
other two is unaltered. Similarly after 3 weeks a fairly active 
evolution of oxygen is still shown on examination. 
The power of evolving oxygen is in very close connexion with 
the presenee of the pigment. Thus in young growths the 
pigment is at first almost or entirely absent. Such show no 
power of evolving oxygen. Also if inoculated on slightly acid 
bouillon, or if after inoculation the cultures are kept for a day 
or two at 35^ C. to 40° C. and then brought to 20? C., the sub- 
sequent growth may remain for a long time, or permanently, 
entirely or almost entirely colourless. Such colourless cultures 
on examination, either by the Bacterium method or by the 
analytical method described later, show no evolution of oxygen. 
Cultures in which a small amount of pigment is present show à 
correspondingly weak power of evolving oxygen. 
The nature and properties of the pigment-substance, though 
Mn colour varies in the different Bacteria from red to indigo-blue, 
18 1m all cases essentially the same. Their insolubility in water, 
and solubility in ether, alcohol, benzol, and chloroform, and the 
changes 9f coloration displayed on treatment with sulphurie 
" nitric acids, show them to belong to the class of pigments 
HS0. d Lipochromes. Thus in all cases with concentrated 
on id e pigment turns bluish green, whilst with N aHO the 
is i polour returns. With HNO, a bluish-green tinge 13 
passe oduced, but this is almost at once further oxidized and 
s through à series of colours until finally it becomes almost 
r quite colourless. 
seo e above 9 Bacteria, as soon as the culture becomes 
actoris corel, the main mass of the pigment is external to the 
diffuse but us to its fatty nature, however, the pigment does not 
part of the MD in close association with and as an integra 
coccus cit reng mi from which it was developed. In Staphylo- 
isolated Bacteria an aurantiaca, and Bacillus brunneus, when t e 
A very faint ts, la are examined with high powers (ys immersion) 
the other ¢ pE of coloration may in many cases be detected, N 
cultures have “preria appear to be perfectly colourless. If the 
een heated to 80° C. or over ether-vapour for 
