418 MR. A. J. EWART ON ASSIMILATORY INHIBITION. 
In the preceding paragraphs we have seen that the function 
of assimilation may be temporarily or permanently inhibited in a 
variety of ways—by cold, by heat, by desiccation, by asphyxiation, 
by etherization, and by treatment with acids, alkalies, or anti- 
pyrin. Boussingault was the first to notice that asphyxiation 
causes a stoppage of assimilation, but erred in supposing that 
the stoppage was always permanent and necessarily involved a 
loss of vitality. Boussingault’s *asphyxie" is really only the 
last stage of asphyxiation. 
Pringsheim has shown by experiments with Chara that it 
is possible to produce a condition of partial asphyxiation or 
inanition during which both assimilation and rotation cease. 
He concludes that inanition is produced by the absence of 
oxygen and that recovery can only take place if a supply of 
oxygen is introduced before inanition has passed into asphyxia, 
but does not take place if the specimen is exposed to light in an 
atmosphere of hydrogen containing a trace of CO,. Working 
from this latter assumption, Pringsheim comes to the conclusion 
that assimilation is a purely protoplasmic function, being hence 
intimately bound up with rotation, ceasing when it ceases and 
recommencing when it recommences, and that the oxygen 
derived from the assimilation of CO, exists in the cell in the 
form of an oxygen-producing substance which undergoes decom- 
position and gives off oxygen on the outer surface of the cell 
only, no free oxygen being present in the interior of the cell*. 
In support of his assumption that an oxygen-producing sub- 
stance is present in every assimilating cell, Pringsheim evidences 
the fact that dead green and non-green cells commonly at death 
show an evolution of oxygen which can be detected by the Bac- 
terium method. This statement evidently required further proof, 
as the movement of B. Termo might be affected by the nutritious 
substances which exude from the dying and contracting cell- 
contents. As a matter of fact, it was found that the nutritious 
substances evolved from a dying cell by exosmosis do aid the 
movement of the Bacteria and enable them to continue moving 
in a closed cell longer than they would have done in water alone, 
but that a distinct evolution of oxygen may take place from a 
dying cell previously actively assimilating. 
In a closed cell in water B. Termo ceases to move in 2 or 
* That free oxygen is actually present in the interior of the cell has now been 
definitely proved. See Pfeffer, “ Oxydations Vorgänge in lebenden Zellen," in 
Abh. Sachs. Ges. Wiss. Leipzig (1889), pp. 375-516. 
