PRESIDENTIAL ADDRESS. 533 



no increase in the transformation of physical energy, but actually with a 

 diminution in the trans formation. Under cover of such an assumption it might 

 be held that this mysterious influence of which I have spoken absorbed instead 

 of contributing energy to the system, or that it diverted energy without loss 

 from one part of the system to another. 



Now, in my opinion, there is no one at the present time who is in a position 

 to discuss the energy transformation of the central nervous system, further, 

 there is certainly no one capable of dealing with such peculiarities as might arise 

 in the energy transformation of that part of it, the brain, which is associated 

 with the mind. There are many points to be cleared up, as, for instance, the 

 extraordinary relationship of the central nervous system to the general muscular 

 system, upon which I might be allowed for a moment to dwell. The fibres of 

 skeletal muscle form the largest site of energy transformation from the oxida- 

 tion of food or fuel, a site in which apparently no such transformation takes 

 place without a coincident exhibition of characteristic muscle function and 

 the performance of some mechanical work, and are dominated in this trans- 

 formation by impulses discharged from the ventral portion of the central nervous 

 system. This exhibition of function is invariably the cause of a despatch of 

 nervous impulses into the central nervous system again, along the nerve-fibres 

 passing into its dorsal portion. Now, since the energy set free in muscle 

 is out of all proportion to the small sum of energy transmitted from the nervous 

 system, it is capable, amongst other things, of despatching back again to the 

 central nervous system a compensating or even an additional sum of energy. 

 The musculature might then be supposed to reinforce the nervous 6ystem. Until 

 such points are given their due importance it would be ridiculous to dogmatise 

 about the energy equations of the central nervous system, and to discuss the 

 amount of energy expended in the performance of movements, or stored in the 

 absence of movements, within this system. 



I will not labour these points, upon which I can throw no light, but put 

 forward this expression of belief rather than opinion, to explain an attitude re- 

 vealed in the remainder of this address, and not as based on evidence or in any 

 way a statement of demonstrated or demonstrable fact. The essential point for 

 the moment is this — that there is some loophole for the view that mind is not 

 directly associated with life or living matter, but only indirectly with certain 

 dispositions of dynamic state that are sometimes present within certain parts of 

 it. It is a point of view not without interest to physiology, since it would 

 leave that science free to consider all phenomena present in such forms of life 

 and living matter as carry no suggestion of an association with mind, as nothing 

 more or less than physico-chemical phenomena, which, when thoroughly investi- 

 gated, would be completely translatable into scientific terms. Then, too, when 

 there is' evidence of mind, the view is that it represents a force acting from 

 without upon what is still no more than matter involved in certain chemical and 

 physical states. Incidents of function would, in such a view, pass straightway 

 into the realms of physical and organic chemistry, requiring special methods of 

 investigation alone, because of the localisation of processes and punctate states 

 in minute microscopical parts not readily removed from their surroundings into 

 selected experimental surroundings of the same value. 



We are at liberty then to deal with this series of physico-chemical experi- 

 ments, boldly giving each observed difference in circumstance a possible import- 

 ance in the determination of observed differences of character, and each difference 

 in character a probable explanation in terms of simple differences in circum- 

 stance; we may boldly consider the causation of variations, and use the term 

 ' natural selection ' as equivalent to the physico-chemical limits to the successful 

 maintenance of each experiment. Let us for example begin with the blood. 



It is at once legitimate, in the first place, to ask how this blood tissue has 

 arisen from variation in the chemical reactions of nuclear material. The argu- 

 ment runs that some ascertainable cause must have produced a material variation 

 which has been preserved by natural selection, and quite probably, too, by the 

 persistence of the cause over some long period in the history of nuclear material. 

 There is no harm for the moment in surveying causes, and temporarily fixing 

 upon one that seems to possess greater appropriateness than any other. There- 

 fore I suggest that we take this main characteristic of nuclear material in the 

 blood tissue, that it is engaged in the production of a pigment, and that the 



