554 



NA rURE 



[October i, 1908 



that it acts "from the blue" on physical and chemical 

 processes. Yet its action was admittedly dependent on 

 jihysical and chemical conditions, such as warmth, th'e 

 presence of oxygen, &c. In fact, no consistent definition 

 was given to the conception of "vital force." It con- 

 sequently never could become a working hypothesis of any 

 value. 'Chieflv on this account, I think, it practically 

 disappeared from Physiology last century. Yet the class of 

 fact which led to the theory of " vital force " is now more 

 prominent than ever ; and what du Bois Reymond called 

 the "spectre" of Vitalism meets us at every turn, thinly 

 disguised under such names as "cell autonomy," "vital 

 processes," &:c. It is useless to shut our eyes and deny 

 the existence of this " spectre." We must fairly face and 

 examine it. 



However difficult it may be to imagine physico-chemical 

 explanations of such processes as respiratory exchange, 

 secretion, muscular activity, &c., there is nothing in the 

 known facts relating to each process taken by itself to 

 preclude the possibility of such explanations. Let us then 

 follow the Euclidean method and assume provisionally that 

 they are nothing but physico-chemical processes. This 

 assumption evidently implies that each of the living cells 

 concerned has a very complex and definite structure varying 

 according to its functions. To take an example, a secreting 

 cell in the kidney may be assumed to have a structure 

 which responds to the stimulus of a certain percentage of 

 urea or sodium chloride in the blood, and reacts in such 

 a manner that energy derived from oxidation is so directed 

 as to perform the work of taking up urea or sodium 

 chloride from the blood and transferring it against varying 

 osmotic pressures from one end of the cell to the other. 

 This mechanism must also be assumed to have the property 

 of maintaining itself in working order, and probably also 

 of reproducing itself under appropriate stimuli, besides also 

 performing various other functions. Its physico-chemical 

 structure must thus be very definite and complex — to an 

 extent which the older physico-chemical theories took no 

 account of. If wc look to' the cells in other parts of the 

 body we are met with the same necessity for assuming 

 complexities of structure which seem to grow in extent 

 with every advance in physiological knowledge, every dis- 

 covery of new substances present within or around the cells, 

 every discovery of new physiological reactions. 



Let us not lose courage, however, but continue to follow 

 the direction in which our assumption leads. In assuming 

 that the bodv is an enormously complex physico-chemical 

 structure we have only begun to face the difficulties of our 

 hypothesis : for we have still to consider how this structure 

 can have originated in accordance with the physico-cheniical 

 theory of life. The adult organism develops from a single 

 cell, the fertilised ovum. It is certain that this cell does 

 not contain in a preformed condition the structure of an 

 adult organism. The conditions of environment in which 

 any particular ovum develops itself are doubtless indefinitely 

 complex from the physico-chemical standpoint, as indeed is 

 the environment of any particular portion of matter existing 

 anywhere. But these conditions also vary almost indefinitely 

 in the case of different ova, whereas the adult organism 

 to which the ovum gives rise reproduces in minute detail 

 the enormously complex characters of the parent organism. 

 We are thus driven to the assumption that the ovum 

 contains within itself a structure which, given certain rela- 

 tively simple conditions in the environment, reacts in such a 

 way as to build up step by step, from materials in the 

 environment, the structure of the adult organism. To effect 

 this the germ-cell must have a structure almost infinitely 

 more definite and complex than that of any cell in the 

 adult organism. DitTicult as it may be to form any con- 

 ception of the mechanism of a secreting cell, it is infinitely 

 more difficult to form the remotest idea of that of a germ- 

 ■cell. 



But we are still only at the beginning of the difficulty. 

 The assumed tremendous mechanism of the germ-cell has 

 lipfn developed, together with the whole of the rest of the 

 parent organism and countless other germ-cells, from a 

 previous germ-cell. What must the " mechanism " of this 

 cell have been? And that of its endless predecessors? We 

 have reached the Euclidean rcductio ad absurdiim. 



I might strengthen my argument by referring to the 

 further difficulty over any physico-chemical conception of 



NO. 2031, VOL. 78] 



what occurs in the sexual fusion of the male and 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. But I have purposely confined my 

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

 more simply the argument 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 con- 

 temporary 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 

 mi.xed 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 disappoint- 

 ing. 



Our aim as physiologists is to render physiological 

 phenomena intelligible — in other words, to obtain genera! 

 conceptions as to their nature. The point now reached is 

 that the conceptions of Physics and Chemistry are insuffi- 

 cient to enable us to understand physiological phenomena. 

 But if so, we need not sit down in despair, for we can 

 look for other working 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 hundred 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 than it appears to be, but that its fundamental 

 hypotheses are only working hypotheses, applicable only so 

 far as they successfully fulfil their purpose. Each different 

 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 yvhich has hitherto been too ill-defined 

 for deliberate scientific employment. It is simply the con- 

 ception 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 activity 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 conceptions of matter and energy, 

 since the apparent matter and energy contained in, or 

 passing through, 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 energy which at present 

 seems to permeate the organic world at all points. 



1 " Treatise concerning the Principles of Human Knowledge," 1710. 



