PKESIDEISTIAL ADDKESS, . 867 



female cell, or in the process of partial reproduction after injury, or in the facts 

 established by Driesch and others with regard to the extraordinary reproductive 

 powers of each cell in developing embryos. Bnt I have purposely confined my 

 references to more simple and well-known facts ; for the more simply the argu- 

 ment can be put, the better. I confess that as a physiologist I am struck with 

 amazement at the manner in which heredity is often discussed by contemporary 

 writers who endeavour to treat the subject from a mechanistic standpoint. 

 Sometimes, indeed, the germ-cell is acknowledged to be a complicated structure, 

 but at other times it is treated as a ' plasma,' which can be mixed with other 

 ' plasma,' divided, or added to, as if for all the world it were so much treacle ! 

 I have tried to place clearly before you the assumptions in connection with heredity 

 which to my mind make the physico-chemical theory of life unthinkable, even if it 

 be tenaciously clung to in connection with those ordinary physiological phenomena 

 where, as already explained, it has proved so disappointing. 



Our aim as physiologists is to render physiological phenomena intelligible — 

 in other words, to obtain general conceptions as to their nature. The point now 

 reached is that the conceptions of Physics and Chemistry are insufficient to enable 

 us to understand physiological phenomena. But if so, we need not sit down in 

 despair, for we can look for other woi-king conceptions. Are we justified in doing 

 this ? I think we are. 



There is a prevalent popular idea that the world as presented to us under the 

 conceptions of Physics and Chemistry is more than our own imperfect conception 

 of reality, and corresponds completely with reality itself. Philosophy has shown 

 us, however, that this idea must be erroneous; for if it were correct, knowledge 

 of such a world would be impossible. This was first clearly pointed out almost 

 two hundi'ed years ago in this city by one of the greatest of Irishmen, George 

 Berkeley, at that time a Fellow of Trinity College.^ The lesson taught by 

 Berkeley, Hume, and their successors is not that Physical Science is of less value 

 tlian it appears to be, but that its fundamental hypotheses are only working 

 hypotheses, applicable only so far as they successfully fulfil their purpose. Each 

 dift'erent science is thus free to employ whatever working hypotheses may prove 

 most useful in interpreting the order of phenomena with which it deals. We 

 are thus perfectly justified in seeking to find a conception of life -which will serve 

 as a better working hypothesis than that of life as a physico-chemical process. 



I venture to think that the conception we are in search of lies very near to 

 hand and is indeed in common use, though in a form which has hitherto been 

 too ill-defined for deliberate scientific employment. It is simply the conception 

 of the living organism, which stands, or ought to stand, in the same relation to 

 Biology as the conceptions of matter and energy to Physics, or of the atom to 

 Chemistry. Let me try to give more definition to this conception. A living 

 organism is distinguished by the fact that in it what we recognise as specific 

 structure is inseparably associated with what we recognise as specific activity. 

 Its activit}"^ expresses itself in the development and maintenance of its structure, 

 which is nothing but the expression of this activity. Its identity as an organism 

 is not physical identity, since from the physical standpoint the material and energy 

 passing through it may be rapidly changing. In recognising it as an organism 

 we are applying an elementary conception which goes deeper than the concep- 

 tions of matter and energy, since the apparent matter and energy contained in, or 

 passing tbrough, or reacting with, the organism are treated as only the sensuous 

 expression of its existence. Even the environment is regarded as in organic 

 relation with the organism, and not as a mere physico-chemical environment. It 

 follows that for Biology we must clearly and boldly claim a higher place than 

 the purely physical sciences can claim in the hierarchy of the sciences — higher 

 because Biology is dealing with a deeper aspect of reality. It must also be the 

 aim of Biology gradually to penetrate behind the sensuous veil of matter and 

 pnergy which at present seems to permeate the organic world at all points. 



Let us now see how the conception just defined can be used as a scientific 



' Treatise concerning the Princiules of Human KnoKledge, 17 JO. 



3 K 2 



