86 SECTIONAL ADDRESSES 
happen is true, but has it, in point of fact, ever occurred under the observa- 
tion of mankind ? Unless a positive answer can be given to this question, 
the belief in the spontaneous origin of living matter seems to be a negation 
of the principles which underlie scientific thought. 
If we decline to accept the spontaneous origin of living from non-living 
matter, there is no particular reason why we should hope to express all 
the properties of an organism in terms of physical laws ; we might just 
as reasonably try to express physical phenomena in terms of biological 
conceptions. It seems more logical to accept the existence of matter in 
two states (the animate and the inanimate) as an initial assumption. 
Some properties are naturally common to matter in either state, and it is 
therefore legitimate to study the so-called physical properties of living 
matter ; but just as the fundamental concepts of physics are based on 
observational facts, so those of biology must conform to the same condi- 
tions. The physicist is not concerned with the origin of inanimate 
matter ; he is content to investigate it as he finds it. The biologist must 
likewise accept the living state as he finds it and not allow his science to 
rest on theories, however spectacular or attractive. It is not easy to 
define Life, but in practice most people will admit that matter in the living 
state possesses characteristics which are fundamentally different from 
those of inanimate objects. 
The central characteristic of living matter is its state of organised 
dynamic structure. This is obvious in all the larger forms of animal life, 
but it is equally true in so-called ‘homogeneous’ protoplasm. This 
important fact emerges from the study of such cells as the eggs of echino- 
derms and molluscs. From a biological point of view, the eggs represent 
not only very remarkable chemical laboratories, but also systems which 
are capable of transforming themselves spontaneously into highly differen- 
tiated organisms. A study of the physical properties of the eggs shows, 
conclusively I think, that the cytoplasm consists of a fluid matrix in which 
lie the granules which are visible under the microscope. ‘The viscosity 
of the fluid matrix has been measured by observing the rate at which 
granules or particles move through the cytoplasmic matrix when exposed 
to a given intensity of centrifugal force—and the value so obtained is 
confirmed by observing the velocity at which such granules redistribute 
themselves spontaneously by Brownian movement. We conclude from 
such observations that the cytoplasm of the cell with all its complicated 
biological properties possesses, in the aggregate, the general properties of 
a liquid and not of a solid. Similarly, the immature nucleus of the odcyte 
has the general properties of a fluid, and yet it proceeds spontaneously 
to form the highly differentiated system seen during meiosis. Within the 
fluid system of the cytoplasm or the nucleus, single molecules or aggregates 
of molecules will distribute themselves at random (just as do the granules 
we can see through the microscope), unless these molecules are subjected 
to suitable restraint. When we try to picture the cell or the nucleus as a 
complex chemical laboratory, it is by no means easy to visualise the type 
of forces which are necessary to hold the various particles or molecules 
in their proper position relative to each other. Were the matrix of the 
cell of a solid nature, the problem would be much simpler. It may be 
suggested that the application of centrifugal force destroys the real struc- 
