Bespiration and Cell Energy. 
411 
evident that the oxygen must be derived from the decomposition of the 
organic substances in the cell. Pfeffer, however, states that oxygen is not 
primarily set free, but that the carbon-dioxide evolved is the end product 
of such abnormal decomposition. This form of respiration is called intra- 
molecular respiration, but, if Pfeffer's statement is true, then the process 
is not one of respiration at all, since oxygen as oxygen is not involved. In 
any case it must be noted that during such conditions all growth ceases 
and abnormal processes of decomposition take place, whereby alcohol and 
other products are formed, until the accumulation of such injurious 
products is sufficient to kill the organism. If oxygen, however, is re- 
admitted early enough ordinary respiration may be re-established and the 
organism will survive. It has been estimated that a plant will use up 
about 50 per cent, of its substance before death ensues. This helps to 
show that free atmospheric oxygen is not necessary to carry on the 
decomposition processes of nutrition. Some of the lower plants amongst 
the Bacteria and Fungi are able, under favourable conditions, to exist for a 
long time without free oxygen. This capability goes so far in some 
Bacteria that no trace of free oxygen is even necessary for their existence, 
whilst some cannot even live in the presence of oxygen. Such organisms 
are called Anaerobes to distinguish them from Aerobes. Concerning the 
carbon-dioxide evolved the question arises, is carbon -dioxide given off 
primarily in the form of carbon-dioxide, or is it only carbon that is given 
off ? In the metabolism of the cell, substances are first decomposed and 
then reconstruction takes place. Most of the components of the de- 
composed materials are used up, especially in plants, but it would appear 
that there is a residual amount of carbon which is either a true residuum 
or carbon in a condition which cannot be utilised. If this carbon is not 
removed it may be that it would interrupt the chemical actions in the cell. 
In any case the carbon is oxidised into carbon-monoxide and then into 
carbon-dioxide and carried off as a gas. This oxidation liberates more 
energy which is available by the protoplasm, and in my opinion this is 
the chief source of energy of all living protoplasm. Plants go to con- 
siderable trouble to get the small amount of carbon-dioxide present in the 
atmosphere, and yet in the metaboHsm of the cell it is given up again 
most readily. Thus a plant sacrifices a large proportion of its food in 
order to obtain the energy necessary in metabolism. Carbon is therefore 
probably set free by the protoplasm for the definite purpose of uniting 
with oxygen and thus supplying energy. A supply of free oxygen has 
thus become a necessity to all living cells. It has been calculated that a 
seedling poppy plant whose dry weight was about half a gram gave off 
55 cubic centimetres of carbon-dioxide in 24 hours, thus liberating 
220 units of heat. This heat is sufficient to raise 22 grams of water 
through 10 degrees Centigrade. All this energy is not used up in the 
