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that a morbid predisposition which has arisen in some 

 individual, whether ancestral or parental, has, by heredity, 

 been transmitted to his offspring, and either intensified by 

 descent, or modified by age, sex, or accessory circumstances. 

 In speaking of diseases as hereditary, I do not mean that 

 the diseases themselves, occurring either in ancestors or 

 parents, are actually transmitted to their offspring (who, 

 under those circumstances, would be born with them), but 

 what is really meant is that a certain organic constitution is 

 inherited by the children, which being likely to undergo 

 pathological development in the ordinary circumstances of 

 life, is therefore described as a constitutional predisposition 

 or tendency to disease. 



If it is admitted, as I have indicated, that every individual 

 is subject to heredity in his physical, mental, and moral 

 constitution, and to such an extent in his physical organisa- 

 tion that the minutest structure of his every organ and tissue 

 is characterised by it it seems to me but a natural sequence 

 that the life-history of his parents' organs and tissues will be 

 re-enacted to some extent, at least, in his own, and that 

 when they have developed organic or tissue derangement or 

 degeneracy of any kind, he, too, will at least have inherited 

 a predisposition to the same. This, I think, may be accepted 

 as a broad statement of a general truth the truthfulness of 

 which is not assailed even when we consider the effect of 

 such modifying factors as individual varieties of age, sex, 

 and circumstances. 



With the object of inquiring how far this view is supported 

 by the records of experience, and of actual disease, I passed 

 in careful review the majority of the diseases " which flesh 

 is heir to," including intra-uterine diseases, diseases of the 

 circulatory and nervous systems, of the respiratory organs, 



