THE CAUSATION OF DISEASE. 32 I 



powerful, and hating hard work. Out of these preceding traits 

 it is not difficult to imagine how the great Abraham came 

 to be inflexible of purpose and strong of will, though indolent 

 — why he was good-natured to excess in his excess of strength 

 — and why he was a great humourist, and, at the same time, 

 a melancholy man." Having thus traced the hereditary influence, 

 the writer proceeds to consider the influence of the E. How 

 often, I would ask, does the pathologist, when investigating 

 the influence of heredity in disease, in the same way try to 

 analyse minutely the several ancestral traits ? It must be 

 acknowledged that it is very seldom. His task, I admit, is 

 much more difficult, for while the mental traits of an indi- 

 vidual are obvious, being, so to speak, on the surface, the 

 same cannot be said of the minute structural characteristics 

 of his several tissues ; but difficulties should not deter from a 

 task when great issues are at stake. 



Writers of fiction are equally ready to recognize the influence 

 of heredity. George Eliot, describing Adam Bede, writes : 

 " He was not an average man; yet such men as he are reared, 

 here and there, in every generation of our peasant artisans, 

 with an inheritance of affections nurtured by a simple family 

 life of common need and common industry, and an inheritance 

 of faculties trained in skilful, courageous labour." 



Seeing, therefore, how thoroughly the influence of heredity 

 upon the mental organization has been recognized by those 

 whose close study of human nature entitles them to speak 

 with authority, it scarcely needed the work of Galton to prove 

 the inheritability of genius. (I say this with no want of 

 appreciation of his most interesting book.) 



To turn now to the physical side, the prominent part 

 played by heredity in the causation of disease will be at once 

 evident if we bear in mind that disease is a morbid inter-action 

 of S and U, and that S is determined almost entirely by here- 

 dity. Strictly speaking, every disease from which an individual 

 suffers is hereditary. Although this may seem to be an 

 exaggeration, the truth of it will presently be apparent. 



We have seen that the offspring is in a large degree the 

 resultant of many ancestral tendencies, and that, could we only 



