THE PRESIDENTIAL ADDRESS. 9 



gence of mind from no' mind, whicli is repeated even in the individual 

 life history. In the nervous system there is what is termed localisa- 

 tion of function, relegation of different work to the system's different 

 parts. This localisation shows mentality, in the usual acceptation of 

 tliat term, noit distributed broadcast throughout the nervous system, but 

 restricted to certain portions of it — thus, among vertebrates to what is 

 called the forebrain, and in higher vertebrates to the relatively newer 

 parts of that forebrain. Its chief, perhaps its sole, seat is a compara- 

 tively modern 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 rest of the system. Simple 

 nei*ve impulses, their summations and interferences, seem the one 

 uniform office of the nerve-system in its non-mental aspect. To pass 

 I'lom 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 incom- 

 mensurable one. We might expect, then, that at the places oi transi- 

 tion from its non-mental to its mental regions the brain would exhibit 

 some striking change of structure. But no; in the mental parts of 

 the brain still nothing ]3ut the same old structural elements, set end 

 to end, suggesting the one function of the transmission and collision of 

 nerve impulses. The structural inter-connections are licher, but that 

 is a merely quantitative' change. 



I do not want, and do not need, to stress our inability at present 

 to deal with mental actions in terms of nervous actions, or vice versa. 

 But facing the relation borne in upon us as existent between them, may 

 we not gain some further appreciation of it by reminding ourselves 

 even biiefiy of certain points of contact between the two? Familiar as 

 such are, I will merely mention rather than dwell upon them. 



One is the so-called expression of the emotions. The mental re- 

 action of an emotion is accompanied by a nervous discharge which is 

 more or less characteristic for each several type of emotion, so that 

 the emotion can be read from its bodily expression. This nervous dis- 

 charge is involuntary, and can affect organs, such as the heart, which 

 the will cannot reach. Then there is the circumstance that the peculiar 

 ways and tricks of the nervous machinery as revealed to us in the stud;v 

 of pure reflex reactions repeat themselves obviously in the working of 

 the machinery to which mental actions are adjunct. The phenomenon 

 of fatigue is common to both, and imposes similar disabilities on both. 

 Nervous exlianstion and mental exhaustion mingle. Then, as offset 

 against this disability, there exists in both the amenability to habit 

 formation, mere repetition within limits rendering a reaction easier 

 and readier. Then, and akin to this, is the oft-remarked trend in both 

 for a reaction to leave behind itself a. trace, an engi-am, a memory, the 

 reflex engram, and the mental memory. 



