140 DR. A. J. EWART ON THE EVOLUTION OF 
on clamping the charcoal is seen to be no longer able to 
evolve sufficient oxygen to cause Bacterium Termo to recommence 
to move. 
With a piece of hemoglobin the size of a small pea, made toa 
paste with water and placed in the chamber, after the current 
has passed through for 4 hour the B. Termo are at rest. On 
clamping in 2-5 minutes the movement recommences and is 
soon quite active. After 10 hours the hemoglobin can still 
evolve sufficient oxygen to cause the B. Termo to move in 10-15 
minutes, and next day a weaker but still quite distinct evolution 
of oxygen can be detected. 
Wood-charcoal, therefore, in an atmosphere of hydrogen 
evolves nearly all its contained oxygen rapidly and suddenly in 
the first hour or so, and the last traces more slowly in the 
succeeding 3 or 4 hours. Oxyhemoglobin, on the other hand, 
evolves its oxygen more slowly at first, but the evolution of 
oxygen remains for along time constant and may persist for 4 
day or more. The evolution of oxygen from a mass of the 
coloured Bacteria is distinctly more active during the first 
hour, but then remains fairly constant for a few hours, then 
gradually weakens, but in some cases after 6 to 8 hours 
is still perceptible. A portion of this difference may be due 
to the greater impermeability of the pasty mass of hemo 
globin employed allowing a longer retention of the stored 
oxygen. 
Hoppe Seyler * states that 100 grammes of oxy hzemoglobin, 
if dissolved in water, can evolve in vacuum 156 c.c. of oxygen 
whereas Hüfner + finds that 1 gramme of oxyhemoglobin ca 
only evolve 1:2 c.c. of oxygen. Apparently oxyhemoglobin can 
hold more oxygen when in solution than when dry ; but even the 
dry hemoglobin seems to have a greater power of occluding 
oxygen than the extracted bacterial pigment has. Thus an 
equal amount of the latter shows only a relatively weak 
evolution of oxygen lasting for a few hours, and intermediate 12 
character between that from charcoal and heemoglobin. There 
can be little doubt, however, that the oxygen occluded by the 
bacterial pigment is held in a similar manner to that in which 
* Hoppe Seyler, Chemische Analyse, 6te Auflage, 1893, p. 275. 
? ; Hüfner, in Zeitschrift f. physiol. Chemie, Bd. i. S. 317 & 386; Bd. iii. $.1 
(1879). 
