306 VEGETABLE PHYSIOLOGY 
Many very complex disturbances set in when a normally 
respiring plant is cut off from a supply of oxygen. Death 
does not immediately supervene, as might almost be expected. 
Instead, the partial asphyxiation or suffocation stimulates 
the protoplasm to set up a new, and perhaps supplementary, 
series of decompositions, resulting in the liberation of 
energy, ag do those of the respiratory process. We have 
already noticed that under such circumstances the exhaling 
stream of carbon dioxide can still be observed. This led 
originally to the view that the protoplasm excited these 
decompositions of some complex substance in the cell to 
obtain oxygen from it, which should replace the oxygen 
whose access had been stopped. The ultimate changes 
were accordingly held to go on with but slight interruption, 
but the source of the oxygen taking part in them was 
different. On this account the process was termed intra- 
molecular respiration. The term is rather an unfortunate 
one, for, as we have seen, the study of the ordinary respira- 
tory processes has shown that the. molecule of the living 
substance is the seat of the changes they involve, and 
hence that all respiration is intramolecular. Moreover, if the 
object of the decomposition is to provide oxygen to replace 
that which has been cut off, these transformations precede 
the actual respiration, which must then be set up as soon 
as the oxygen is liberated as suggested. Many botanists 
now prefer to speak of decompositions taking place in the 
absence of a supply of free oxygen as anaerobic respiration. 
They thus include as respiratory changes all the decomposi- 
tions primarily intended to liberate energy, and divide them 
into those which are aerobic or dependent on oxygen, and 
those which are anaerobic. The latter need not involve 
the co-operation of oxygen in the disruption of the molecule. 
The object sought is energy and not oxygen. 
It is uncertain how far the auto-decomposition of proto- 
plasm is concerned in these anaerobic respiratory processes. 
Probably not to any great extent ; it is more likely that it 
secures the decomposition of other substances without being 
