350 



SCIENCE 



[Vol. LVI, No. 1448 



though not to normal cells. The following of 

 all elues of diit'erence between the mechanism 

 of malignant growth and of normal is fraught 

 with importance 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 time when it actually 

 reaches the muscle or skin, no actual perform- 

 ance of nerve-function can take place. "What 

 is constructed is functionally useless until the 

 whole is complete. So similarly with much of 

 the construction of the embryo in the womb for 

 pui'poses of a different life after emergence 

 from the womb; 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 sep- 

 arated, let alone ere hurt or even light can 

 reach it; of the butterfly's wing within the 

 chrysalis for future flight. 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 fore- 

 stall and meet a future function. It is a mech- 

 anism against the seeming prescience of which 

 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 reac- 

 tions; 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 

 mechanisrii. If "to know" be "to know the 

 causes" we must confess to want of. knowledge 

 of how its mechanism is contrived. 



If we knew the whole "how" of the produc- 

 tion 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 com- 

 pletely as do inorganic systems, will the living 

 animal present no other problematical aspect? 

 The dog, oxxi household friend — do we exhaust 

 its aspects if in assessing its sum-total we omit 

 its mind? A merely reflex pet would give little 

 pleasure even to 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 chosen partly 

 at the suggestion of a late member of it. Dr. 

 Rivers, the loss of whom we all deplore. As a 

 biologist he v»wed mind as a (biological factor. 

 Keeping 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 ordi- 

 narily received as such, mind does not seem ta 

 attach to life, however complex, where there is 

 no nervous system, nor even where that system, 

 though present, is little developed. Mind be- 

 comes more recognizable the more the nerve- 

 system is developed; hence the difficulty of the 

 twilit emergence of mind from no mind, which 

 is repeated even in the individual life history. 

 In the nervous system there is what is termed 

 localization of function — relegation of different 

 works to the system's different parts. This 

 localization shows mentality, in the usuid ac- 

 eeption of that term, not distributed broad- 

 cast throughout the nervous system, but re- 

 stricted to certain portions of it; for example, 

 am.ong vertebrates to what is called the fore- 

 brain, and in higher vertebrates to the rela- 

 tively newer parts of that forebrain. Its chief, 

 perhaps its sole, seat is a comparatively mod- 

 ern nervous structure superposed on the non- 

 mental and more ancient other nervous parts. 

 The so-to-say mental portion of the system is 

 placed so that its commerce with the body and 

 the external world occurs only through the 

 archaic non-mental remainder of the system. 

 Simple nerve impulses, their summations and 

 interferences, seem the one uniform office of 

 the nerve-system in its non-mental aspect. To 

 pass from a nerve impulse to a psychical event, 

 a sense-impression, percept, or emotion is, as 

 it were, to step from one world to another and 

 incommensurable one. We might expect, then, 

 that at the places of transition from its non- 

 mental to its mental regions the ibrain would 

 exhibit some striking change of structure. But 

 it is not so; in the mental parts of the brain 

 there is nothing but the same old structural 

 elements, set end to end, suggesting the one 

 function of the transmission and collision of 

 nerve impulses. The structural inter-connec- 

 tions are richer, but that is merely a quantita- 

 tive change. 



