8 THE PRESIDENTIAL ADDRESS. 



make the soil in which they grow poisonous to themselves, though not 

 to normal cells. The following of all clues of difference between the 

 mechanism of malignant growth and of normal is fraught with import- 

 ance which may be practical as well as theoretical. 



The regenerating nerve rebuilds to a plan that spells for future 

 function. But throughout all its steps prior to the actual reaching the 

 muscle or skin no actual performance of nerve-function can take place. 

 What is constructed is functionally useless until the whole is complete. 

 So, similarly, with much of the const-ruction of the embryo in the womb 

 for purposes of a different life after emergence from the womb; with 

 the construction of the butterfly's wing within the chrysalis for future 

 flight ; of the lung for air-breathing after birth ; of the reflex contraction 

 in the foetal child of the eyelids to protect the eye long before the two 

 eyelids have been separated, let alone ere hurt or even light can reach it. 

 The nervous system in its repair, as in its original growth, shows us 

 a mechanism working through phases of non- functioning preparation 

 in order to forestall and meet a future function. It is a mechanism 

 against whose seeming prescience is to be set its fallibility and its 

 limitations. The how of its working is at present chiefly traceable to us 

 in the steps of its results rather than in comprehension of its intimate 

 reactions; as to its mechanism, perhaps the point of chief import for us 

 here is that those who are closest students of it still regard it as a 

 mechanism. But if to know be to know the causes we must confess 

 to want of knowledge of how its mechanism is contrived. 



And if we knew the whole how of tlie production of the body from 

 egg to adult, and if we admit that every item of its organic machinery 

 runs on physical and chemical rules as completely ag do inorganic 

 systems, will the living animal present no other problematical aspect? 

 The dog, our household friend — do we exhaust its aspects if in assessing 

 its sum-total we omit its mind? A merely reflex pet would please little 

 even the fondest of us. True, our acquaintance with other mind than 

 our own can only be by inference. We may even hold that mind as an 

 object of study does not come under the rubric of Natural Science at all. 

 But this Association has its Section of Psychology, and my theme of 

 to-night was partly chosen at the instance of a late member of it. Dr. 

 Eivers, the loss of whom we all deplore. As a biologist he viewed mind 

 as a biological factor. The keeping of mind and body apart for certain 

 analytic purposes must not allow us to forget their being set together 

 when we assess as a whole even a single animal life. 



Taking as manifestations of mind those ordinarily received as such, 

 mind does not seem to attach to life, however complex, where there is 

 no nervous system, nor even where that system, though present, is 

 quite scantily developed. Mind becoimes more recognisable the more 

 developed the nerve-system. Hence the difficulty of the twilit emer- 



