president's address. 821 



attempt may be of service in anew directing your own thoughts 

 ujjon subjects which cannot entirely or for long be kept in the 

 background. 



In order to bring under our consideration some of the governing 

 ideas of modern biology, it is well and even necessary to look 

 backwards toward the earlier stages of their growth. 



For our present purpose, it is unnecessary to attempt a complete 

 historical retrospect. 



From the scientific awakening which characterised the period 

 of the Renaissance up to the early part of the eighteenth century 

 the progress of natural science had been steady and assured. 



But when we attempt to realise the state of biological thought 

 in what may be called the Linnean period of the eighteenth century 

 it is necessary to have regard to the conditions imposed upon it 

 by the state of knowledge in other departments, and by the 

 restrictions of a very limited technique of investigation. 



It is difficult fully to realise the aspect which the problems of 

 biology presented to men for whom nearly the whole of modern 

 chemistry, and so much of the methods and results of experimental 

 physics, were still non-existent. Microscopy, too, though practised, 

 it is true, as early as the previous century, had made little 

 progress ; and though it had been the means of revealing a 

 number of additional structural facts, it cannot be said to have 

 taken rank as a reliable or habitual instrument of research. 

 Of the minute structural characters of living tissue, hardly 

 anything at all was known, whilst the processes and reactions of 

 which these tissues are at once the seat and the essential 

 mechanism were likewise wrapped in the profoundest obscurity. 

 And if these internal relationships of organism were little under- 

 stood, the interpretation of the external relationship subsisting 

 between organism and organism both in structure and in function 

 was likewise profoundly limited and restricted by the current 

 conceptions of the i-elations between past and present in the 

 world's histor3^ 



The Copernican revolution in astronomy has been rightly 



regarded as a symbol and an expression of a far more general 

 53 



