332 THE POPULAR SCIENCE MONTHLY. 



Genius is a natural force which possesses a value only in so far as 

 work has been expended in developing and applying it ; this work 

 produces values by consuming values. 



All mental labor is at the same time brain-labor. The brain con- 

 sumes a certain amount of food-material. Of course, all the other 

 involuntary bodily movements which go on simultaneously with the 

 brain-movements, as also the necessary periods of rest, must be taken 

 into account in estimating the value of the products of mental labor. 



Here, too, a definite amount of food-substances gives a definite 

 quantity of (mental) work. Das Ausland. 







ON HEEEDITY IN NERVOUS DISEASES. 



By EUGENE DUPUY, M. D. 



THE facts which I propose to consider in this paper have been 

 brought to light by means of the experimental method. They 

 are very interesting, both physiologically and psychologically viewed. 

 I shall occupy myself with the physiological aspects only, and their 

 bearing on human pathology. Psychology is beyond my province. 

 Moreover, I conform myself to the saying of Montaigne, that deduc- 

 tions are very difficult to draw in psychological science, for ''' comtnent 

 cognoit on la semblance de ce de quoi on ne cognoit point Vessence? " ^ 



Most of the facts observed, of hereditary transmission of nervous 

 disorders, were put on record many years ago by my eminent friend 

 and teacher Dr. Brown-Sequard. Some I have observed, together 

 with him, during the years that I was his assistant, and others I have 

 discovered quite lately. 



The disorders which were inherited had all been artificially in- 

 duced in animals for the sake of experimentation. Very great care 

 was taken in all cases to avoid causes of error, and I am positive that 

 they were got rid of completely. 



It will be seen that lesions which affect not onlv nutrition of 

 parts, but also the higher functions of the nervous system, can be de- 

 veloped by hereditary tendencies, when artificially provoked, through 

 those nerves which minister to organic functions belonging to the 

 so-called sympathetic system. 



It is well known that a system of nerves exists in all animals 

 which have a circulation, and which apparently has no other functions 

 but to control the blood-vessels, to regulate the flow of the blood 

 through them. This nervous system is called, therefore, the vaso- 

 motor system; it is also termed the sympathetic. 



' How can one know the like of that of which one knows not the essence ? 



