648 POPULAR SCIENCE MONTHLY. 



WHEN CHARACTER IS FORMED. 



BY M. V. O'SHEA, 



PROFESSOR ELECT OF THE SCIENCE AND ART OF TEACHING, UNIVERSITY OF WISCONSIN. 



THE results of late researches in physiological and experi- 

 mental psychology contribute much toward a rational ex- 

 planation of the causes of abnormal and deficient mental char- 

 acteristics in childhood. To begin with, it is now satisfactorily 

 shown that mental action is accompanied by the expenditure of 

 energy derived from the breaking down of highly unstable chem- 

 ical compounds in cerebral nerve* cells. The brain has come to 

 be regarded as a storehouse of nerve power ; and when too severe 

 or prolonged demands have been made upon it the cells become 

 much depleted of their contents, and there results a condition of 

 brain tire or fatigue. The process of depletion has been studied 

 with great care in the case of the frog by Dr. Hodge,* of Clark 



DIAGRAM A, showing changes observed in the nucleus of the living sympathetic nerve cell of 

 the frog, as the result of direct electrical stimulation (Hodge, after Donaldson f). After 

 six hours and forty-nine minutes of stimulation, the nucleus () is seen to be reduced to 

 less than one half its size when the stimulation began. 



University, and some of his results are shown in the accompany- 

 ing Diagram A. 



While no similar observations have been made upon human 

 beings, for obvious reasons, yet it seems reasonable that the same 

 law holds here in regard to the expenditure of nerve energy by 

 physical or mental work. 



It is evident that the law of the conservation of energy is im- 

 plied in this phenomenon, and the accompanying diagrams may 

 serve to make clear the method of its application. In Diagram B 

 there is shown leading to the very heart of the nerve cell a fila- 

 ment, N, whose office is to carry messages in the form of stimuli 

 from the world without ; and leading from each cell are a num- 

 ber of avenues or passageways, D, through which may run off to 

 other cells or muscles the energy set free by the advent of some 

 sense stimulus or by the processes of thought and feeling. A 

 very slight stimulus may in certain instances unloose a relatively 



* For a detailed description of the method of making the study, with results, see Hodge, 

 Some Effects of Electrically Stimulating Ganglion Cells. American Journal of Psychology, 

 vol. ii, p. 3 et seq. f The Growth of the Brain, p. 320. 



