THE PRESIDENTIAL ADDRESS 15 
of such activities. It must learn to describe in objective chemical 
terms precisely how and where such molecules as those of hormones 
and vitamins intrude into the chemical events of metabolism. It is 
indeed now beginning this task which is by no means outside the 
scope of its methods. Efforts of this and of similar kind cannot 
fail to be associated with a steady increase in knowledge of the whole 
field of chemical organisation in living organisms, and to this increase 
we look forward with confidence. The promise is there. Present 
methods can still go far, but I am convinced that progress of the kind 
is about to gain great impetus from the application of those new 
methods of research which chemistry is inheriting from physics: 
X-ray analysis; the current studies of unimolecular surface films 
and of chemical reactions at surfaces ; modern spectroscopy ; the 
quantitative developments of photo-chemistry ; no branch of 
inquiry stands to gain more from such advances in technique than 
does biochemistry at its present stage. Especially is this true in the 
case of the colloidal structure of living systems, of which in this 
Address I have said so little. 
IV. 
As an experimental science, biochemistry, like classical physi- 
ology, and much of experimental biology, has obtained, and must 
continue to obtain, many of its data from studying parts of the 
organism in isolation, but parts in which dynamic events continue. 
Though fortunately it has also methods of studying reactions as they 
occur in intact living cells, intact tissues, and, of course, in the intact 
animal, it is still entitled to claim that its studies of parts are con- 
sistently developing its grasp of the Wholes it desires to describe, 
however remote that grasp may be from finality. Justification for 
any such claim has been challenged in advance from a certain philo- 
sophic standpoint. Not from that of General Smuts, though in his 
powerful Address which signalised our centenary meeting he, like 
many philosophers to-day, emphasised the importance of properties 
which emerge from systems in their integrity, bidding us remember 
that a part while in the whole is not the same as the part in isolation. 
He hastened to admit in a subsequent speech, however, that for 
experimental biology, as for any other branch of science, it was 
logical and necessary to approach the whole through its parts. Nor 
again is the claim challenged from the standpoint of such a teacher 
as A. N. Whitehead, though in his philosophy of organic mechanism 
there is no real entity of any kind without internal and multiple 
relations, and each whole is more than the sum of its parts. I never- 
theless find ad hoc statements in his writings which directly encourage 
the methods of biochemistry. In the teachings of J. S. Haldane, 
however, the value of such methods have long been directly 
