88 SECTIONAL ADDRESSES 
their viability—the single cell behaves, in fact, as though it represented a 
large population of much smaller units of activity. 
If we accept the view that the fundamental unit of life is extremely 
small, we can see that mechanical disturbances throughout a suspension 
of such units may induce no very far-reaching results. The conception 
of protoplasm as an emulsion of small vital units suspended in a fluid 
system is perhaps the most satisfactory picture we can derive from available 
facts ; but it breaks down when we try to think of the mechanism whereby 
the cell differentiates itself as a whole—for here we must postulate some 
form of co-ordinated relationship between individual units. If, however, 
we shelve this difficulty for the moment and accept the general conception 
that ‘ vital’ properties are associated with very small units of structure, 
a variable number of which are normally aggregated together as a suspen- 
sion to form a single cell—it is obvious that we must exercise very great 
caution in the application of the statistical laws of physics in describing 
the properties of the fundamental units of life. ‘The only legitimate laws 
are those applicable to the behaviour of single units of activity. So far 
as I can form an opinion, such determinate laws have not yet been forth- 
coming. I am inclined to think that the intrinsic properties of living 
matter are as mysterious and as fundamental as the intrinsic properties 
of the molecule of a radio-active substance : when the physicist can tell 
us why one particular molecule explodes and why another goes on existing, 
I venture to think that we can begin to consider the possibility of defining 
the fundamental properties of living protoplasm in physical terms. At 
present, however, the physicist seems more inclined to define physical phe- 
nomena in terms of biological conceptions, for, according to M. Poincaré 
and others, ‘modern physics is presenting us with apparent examples 
of spontaneity and foresight.’ For the moment, however, we must con- 
clude that although physical methods have provided important facts con- 
cerning the state of living material, they have not as yet thrown much light 
on its fundamental properties. 
If we now turn to the behaviour of an echinoderm egg-cell after fertili- 
sation, it is again possible to define certain physical characteristics. We 
can observe changes in the mechanical properties of localised regions of 
the cell and of the nucleus, but we have no adequate picture of how these 
events are initiated. We are, however, acutely conscious of the high 
regulative power of the whole system. If we destroy, by mechanical or 
other means, the astral radiations seen in the cell at the anaphase of mitosis, 
these structures are regenerated in what we can reasonably call the right 
place at the right time. The whole process of nuclear and cell divi- 
sion, when regarded impartially as a physical event, represents an orderly 
process of formation of structural elements—and has physical attributes 
similar to those which characterise the formation of an inanimate machine 
from unorganised material. All attempts to define the mechanism 
whereby this orderly process of segregation is initiated, in terms of physical 
units, are, in my opinion, fanciful. It is more reasonable, at present, to 
regard such powers of effecting an orderly distribution of material as an 
intrinsic and fundamental property of living matter. The operation of 
this power no more involves disobedience of physical or chemical laws 
than does the manufacture of a motor car. 
