512 POPULAR SCIENCE MONTHLY. 



will be the resultant of any given present impression modified by 

 others previously received and treasured up in memory, as we say. 

 To accomplish this really great feat, Nature had to devise an elabo- 

 rate contrivance, interposed between incoming messages and out- 

 going impulses, to act as a moderator or transformer of a very ex- 

 traordinary and intricate character — the central nervous system, 

 comprising the brain and spinal cord. That it may be able to meet 

 the requirements of its office, this system must be equipped with two 

 principal kinds of apparatus — cells, which will serve as storehouses 

 of energy to be employed in keeping the machinery running, and 

 association fibers or pathways, which will put any one cell into com- 

 munication with others in the cerebral community. 



The item which will engage our attention principally here re- 

 lates to the primary function of the nerve cell — to store up vital 

 forces in the form of highly unstable chemical compounds,* which 

 may upon slight disturbance be broken down, the static energy rep- 

 resented in their union thus becoming dynamic. Those who have 

 given special attention to the matter seem to agree that all activity, 

 physical as well as mental, involves the expenditure of a portion of 

 this energy. f It may perhaps be mentioned in passing that when 

 this conception was first being presented some persons hastily con- 

 structed the theory that what people had been calling mind was 

 nothing more nor less than a certain mode of manifestation of this 

 mysterious but yet physical force. Wliile abundant evidence, 

 gained from various sciences by recent research, leads one to the con- 

 viction that in some unknown manner psychical and neural processes 

 are closely co-ordinated, yet not a single investigator of standing 

 claims that they«are identical. There is doubtless among some in 

 our day too great a tendency, unconscious though it may be for the 

 most part, to declare that a description of the physical correlates 

 or antecedents of mental phenomena fully accounts for the latter 

 in respect alike of their nature and their modes of manifestation; 

 but those who find themselves coming to such conclusions might be 

 both interested in and benefited by examining the opinions of great 

 naturalists and psychologists who have reflected long and profoundly 

 upon the world-old problem of the connections between body and 

 mind — such men as Lotze,:]: Darwin,* Romanes, || "Wallace,^ Fiske,0 



* For chemical formulae of some of the compounds, see Ladd, Outlines of Physiological 

 Psychologj', p. 13. 



f For the opinions of investigators, as Mosso, Lombard, Maggiora, Kracplin, and others, 

 Bee Pedagogical Seminary, vol. ii. No. 1, pp. 13-17 ; Scripture, The New Psycholog)', chapter 

 xvi ; and Educational Review, vol. xv, pp. 246 et seq. 



X Microcosmus, p. 162. 



* Descent of Man, p. 66. | Mental Evolution in Man, pp. 213 et xeq. 



^ Darwinism, p. 469. ^ Destmy of Man in the Light of his Origin. 



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