BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 
LEICESTER, 1933. 
THE PRESIDENTIAL ADDRESS 
SOME CHEMICAL ASPECTS OF LIFE 
BY 
SIR FREDERICK GOWLAND HOPKINS, PRES.R.S., 
PRESIDENT OF THE ASSOCIATION. 
Tt 
Tue British Association returns to Leicester with assurance of 
a welcome as warm as that received twenty-six years ago, and of 
hospitality as generous. The renewed invitation and the ready 
acceptance speak of mutual appreciation born of the earlier experi- 
ence. Hosts and guests have to-day reasons for mutual congratu- 
lations. ‘The Association on its second visit finds Leicester altered 
in important ways. It comes now to a city duly chartered and the 
seat of a bishopric. It finds there a centre of learning, many fine 
buildings which did not exist on the occasion of the first visit, and 
many other evidences of civic enterprise. The citizens of Leicester 
on the other hand will know that since they last entertained it the 
Association has celebrated its centenary, has four times visited 
distant parts of the Empire, and has maintained unabated through 
the years its useful and important activities. 
In 1907 the occupant of the Presidential Chair was, as you know, 
Sir David Gill, the eminent astonomer who, unhappily, like many 
who listened to his address, is with us no more. Sir David dealt 
in that address with aspects of science characterised by the use of 
very exact measurement. The exactitude which he prized and 
praised has since been developed by modern physics and is now so 
great that its methods have real esthetic beauty. In contrast I 
have to deal with a branch of experimental science which, because 
it is concerned with living organisms, is in respect of measurement 
on a different plane. Of the very essence of biological systems is 
an ineludable complexity, and exact measurement calls for condi- 
tions here unattainable. Many may think, indeed, though I am 
B 
