72 G. F. C. SEARLE, M.A., F.B.S., ON THE 
possible, the universe will be physically and chemically inert 
in simple words we may say that it will be dead. 
The power of chemical combination of the carbon of coal with 
the oxygen of the air is a great reserve of energy, but in a few 
generations this source of wealth for England will be practically 
exhausted, and then the humblest households will learn by the 
experience of hardships something of the meaning of the loss of 
availability of energy. 
When the operations of the physical laws are traced back- 
wards into past time, they lead to greater and greater availability 
of energy. But there is a limit to ‘this process, for the total sum 
of energy is limited. Speaking generally, the rate at which 
redistributions of energy occur increases with the availability of 
the energy, but even if the rate of loss of availability had never 
been greater than at present we should, in going back, arrive in 
a finite time at a state in which all the energy was, so tc speak, 
in one basket. We thus conclude that only a finite number 
of years has elapsed since the creation of the universe. 
The existence of radio-active substances points to the same 
eenclusion. For since uranium is continually being transformed 
into other substances, and since an appreciable quantity of 
uranium is still left, only a finite number of years has elapsed: 
since uranium was first formed. 
§ 12. Life and Matter—So far we have considered matter 
apart from life. But on the earth there are living organisms. 
ranging from lowly bacteria to stately trees and splendid 
animais and man himself. The bodies of these organisms are 
composed of some of those elements of which inanimate objects. 
are formed, and to that extent living organisms are identical in 
nature with the inanimate world around them. But itis evident. 
that there is a profound difference between life and matter, in 
that hfe involves individuality. Life is capable of employing’ 
the molecules of various elements to form the organism and 
to maintain it as the abode of life for a longer or shorter time,. 
but the organism does not always consist of the same molecules, 
for it is continually taking in some molecules, and rejecting 
others. Thus, for instance, “after the carbon which an animal 
takes in as a constituent of its food has been assimilated, it 
is combined in the body with the oxygen taken in from the 
air and the resulting carbonic acid gas is breathed out. Both 
the carbon and the oxygen form parts of the body for a time,. 
but only fora time. Yet the life of the individual preserves 
its identity, though the body which it controls is never, for two- 
minutes together, composed of exactly the same molecules. 
