126 DR. A. J. EWART ON THE EVOLUTION OF 
ciently strong to repel Spirillum, in accordance with the general 
rule that an oxygen partial pressure, which suffices to keep 
Bacterium Termo in active movement, will repel Sp?rillum. 
It was also found that this phenomenon was by no means 
restricted to Bacillus brunneus, but is also shown by a number 
of other coloured Bacteria. Thus in Bacillus cinnabareus, 
Flügge (vermilion) ; Bacillus janthinus, Zopf (indigo-blue); 
Staphylococcus citreus, List (yellow); Micrococcus agilis, Ali 
Cohen (eoral-red) ; and Sarcina aurantiaca, Flügge (brownish- 
y«llow), the evolution of oxygen is as active, or nearly as active, 
as in Bacillus brunneus, Adametz; but in Sarcina rosea, Flügge 
(pink), and Diplococcus roseus, Fliigge (rose-pink), is weaker, and 
in Sarcina lutea, Flügge (yellow), is much weaker *. 
Definite proof that the exciting cause of the movement of 
Bacterium Termo is really oxygen was obtained in the following 
manner :—A small portion, about the size of a lentil or split pea, 
of the coloured bacterium to be examined is enclosed in a small 
gas-chamber, at first Ranvier-Prazmoski's being used, but later 
solely a special chamber devised by Prof. Pfeffer. On the 
upper surface a cover-glass, having on its under surface 4 
hanging-drop of B. Termo, is fixed and sealed with vaseline-wat 
A current of pure H t is then led through until the B. Termo 
come to rest, when the tubes leading to and fro from the gas 
chamber are closed by clamps. In from one to several minutes 
the B. Termo recommence to move and are soon in active move 
ment. This stoppage and recommencement can be repeated 
time after time. It follows, therefore, that the coloured Bacteria 
examined have the property of evolving a gaseous substance 
which causes B. Termo to move actively, the gas necessarily 
being oxygen. An additional proof that the gas evolved i 
oxygen is afforded by the fact that it is capable of causing 
reduced indigo-carmine to turn blue again. This is demor 
strated as follows:—A current of hydrogen is passed through 
3 flasks kept submersed under water. The Ist and 3rd of thes? 
contain a solution of reduced indigo-carmine to which a little 
* All of these Bacteria grow best on peptone agar, with or without sg" 
and at 20? C. to 959 C, 
t In addition to the usual purifying-tubes, the H is passed over prog 
and KHO. The surface of the acids in the Kipp's generating spain 
covered with paraffin liquidum, whilst the purifying-tubes and all india-rubb 
connexions are kept immersed under water. 
