92 SECTIONAL ADDRESSES 
accept the conventions attached to the laws and agree to ignore such events 
as are improbable although they may conceivably occur. From this 
point of view, the spontaneous origin of living from inanimate matter 
must be regarded as a highly improbable event, and as such can be assumed 
not to have occurred. Similarly, the development of an organism from 
so-called undifferentiated protoplasm involves processes which are entirely 
without parallel in inanimate nature. So long as this state of our know- 
ledge persists, it is dangerous to assume that the statistical laws of physics 
can satisfactorily describe all biological events. Our knowledge of the 
physical and biological properties of living matter suggests that the 
fundamental unit of structure is extremely small, and that it contains 
potentialities for change which are unique in the universe. These pro- 
perties we must accept as fundamental axioms of our science which may 
or may not prove (in the future) to have their parallel in the physical 
world. It may seem presumptuous for the biologist to set up postulates 
peculiar to his own sphere; it would be more fitting perhaps for him to 
accept, with medieval humility, the assumptions of his physical brethren. 
One wonders, however, at times whether the concepts of intrinsic 
organisation and of emergent evolution are entirely absent from modern 
physics. Even if this is not the case, we can fortify ourselves by the 
knowledge that physics has from time to time changed its fundamental 
assumptions with advantage to itself and to the world. Those biologists 
who are inclined to accept the views I have ventured to put forward 
may be encouraged by the remark of Prof. Niels Bohr which very 
recently came to my notice. He says: ‘ The existence of life must 
be considered as an elementary fact that cannot be explained, but must 
be taken as a starting-point in biology, in a similar way as the quantum of 
action, which appears as an irrational element from the point of view of 
classical mechanical physics, taken together with the existence of the 
elementary particles, forms the foundation of atomic physics.’ 
Not infrequently the physiologist can restrict his interest to the physical 
properties of isolated organs—the origin of which does not concern him. 
The zoologist, on the other hand, knows that the beautifully adapted 
mechanism known as an ‘ organ ’ was evolved from a system unlike itself 
and may, in turn, initiate something new. For this reason, he cannot 
afford to forget what may be called the ‘ intrinsic potentiality of the living 
organism.’ He may or may not be able to use this conception as a 
guide to more adequate observations, but it should be constantly in his 
mind. Experimental zoology can be divided into two types of study : 
(1) the investigation of the physical and the chemical properties of living 
organisms ; (2) a study of the intrinsic potentialities of living matter, 
revealing as it does a co-ordination of events which is without inani- 
mate parallel. In the first type of work we must use each new weapon 
which the physicist can give us. In the second type of work, however, 
biology must be the mistress and not the servant of physics or of chemistry 
—she must make her own foundations, and build on them fearlessly, 
prepared to change her views, if need be, but not prepared to force the 
wine of life into bottles which were designed for use in the simpler and 
less intoxicating fields of chemical science. 
