OXYGEN FROM COLOURED BACTERIA. 125 
testing the observations made by Engelmann upon green and 
purple Bacteria, that the following investigation was undertaken, 
the results of which seem to make clear the function of the 
pigment in certain of the Bacteria examined. 
If a quantity of a certain brown bacterium, Bacillus brunneus, 
is enclosed along with Bacterium Termo in a cover-glass prepa- 
ration and ringed with vaseline, it is at once seen that the B. Termo 
remain in active movement for a considerable time in the neigh- 
bourhood of the masses of Bacillus brunneus. The most con- 
venient method of demonstrating this phenomenon is by mixing a 
small quantity of B. brunneus, taken from an agar culture by 
means of a sterilized platinum spatula, with a small drop of cool 
but still fluid gelatine ona slide. When solidified, a drop of water 
containing active Bacterium Termo is added, and the whole is at 
once covered, all air-bubbles being excluded and ringed as usual. 
Round the edges of the gelatine, and especially in any bays or 
indentations which may be present, the B. Termo continue in at 
first very active movement, which gradually becomes weaker and 
finally, after several hours, ceases. If the gelatine is made in 
ring form, the B. Termo move with about equal rapidity on the 
inner and outer sides of the ring. There is hence no error due 
to any diffusion of oxygen from outside through the ringing of 
Vaseline. 
A possibility of error is that the gelatine in such preparations 
id be an exciting or aiding cause for the movement of B. Termo, 
MAU time at least. In preparations made, however, with 
minutes. » gelatine alone, all movement ceases in a few (5-10) 
caused by second possibility is that the movement may be 
due to M some unknown excrete bacterial product, and not be 
filtered exuded d It preparations are made with a drop of the 
with Bacteri we from an agar culture of Bacillus brunneus, or 
minutes, in af which have been heated to 100° c. for a few 
Fresh gelatine M minutes the Bacterium Termo is entirely at rest. 
for 15 to 30 preparations, which have been soaked in water 
: , ^" mmutes, show, on adding B. Termo and closing, a 
quite active movement as usual ° 
An additi se, Ut 
additional indication that the exciting cause of the move- 
ment is oxygen is aq Loop AO. D 
introd afforded by the fact, that if Spirilla are 
uced these collect at a distance from the edge of the 
gelatine, after several h a distance from the edg 
touching it Th era ours coming nearer and nearer and finally 
| € evolution of oxygen is therefore at first sufb- 
