Residual Vitality. 37 
wetted it produces abundant C0 2 and respires for some hours just 
as if it were germinating normally. On the other hand disintegra¬ 
tion is at once fatal to the phosphorescence of luminous bacteria, 
a phenomenon dependent on the presence of oxygen. Macfadyen 
showed this in an ingenious way. He found that this Bacterium, 
like most others is quite uninjured by extreme cold even by being 
dipped straight into liquid hydrogen though at such a temperature 
it of course ceases to be luminous. On being removed from the 
liquid it at once begins to glow again if whole, but if it is 
mechanically disintegrated at the temperature of liquid hydrogen 
then on withdrawal it never recovers its luminosity. 
Friedel was the first, in June 1901, to assert the extraction 
from leaf-cells of spinach, of a substance which was he proposed 
to regard as an enzyme, capable in the presence of suspended 
chlorophyll and in the light, of decomposing C0 2 and producing 
oxygen. The enzyme is prepared by extracting with glycerin, 
precipitating with alcohol and dissolving the flocculent precipitate 
in water. The chlorophyll powder is obtained by drying spinach 
leaves at 100'C and powdering them. Friedel states that neither 
of these substances produces oxygen without the other and that 
the mixture only gives positive results in the summer. Harroy and 
Herzog working in a similar way state that they could not obtain 
any positive results even in summer. 
Macchiati asserts that he obtains positive results, often of 
considerable magnitude, but is opposed to Friedel for he holds that 
the leaf-powder dried at 100"C will work freely when suspended 
in water, giving off bubbles of gas which are collected in a tube and 
analysed. Both authors fail to state the absolute amounts of 
oxygen which they obtained and generally speaking the presentation 
of the facts is confused and unsatisfactory. 
About the same time as Friedel, Beyerinck independently 
approached the subject in another way. Instead of gasometric 
methods he used the extraordinarily sensitive test for oxygen which 
is provided by phosphorescent bacteria. Having pounded up fresh 
leaves in a mortar with some water, he filtered the extract into a 
tube, filled it up with a bouillon culture of the Bacterium and sealed 
it hermetically. The Bacterium glows until the oxygen in solution 
is used up and then all is dark. If the tube is placed in the sun for 
a minute, enough oxygen is formed, by photo-synthesis by what 
Beyerinck considered to be “dissolved protoplasm” and suspended 
chlorophyll, to keep the Bacterium phosphorescent for several 
