Address on heredity in relation to insanity, given to the members of the London County Council, at the County Hall, S.W., on June 26th, 1912 / by F.W. Mott.

  • Mott, F. W. (Frederick Walker), 1853-1926
Date:
[1912?]
Catalogue details

Licence: In copyright

Credit: Address on heredity in relation to insanity, given to the members of the London County Council, at the County Hall, S.W., on June 26th, 1912 / by F.W. Mott. Source: Wellcome Collection.

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    from each parent (2 and o), one sixteenth from each grandparent^ and so oip the sum of tlie total inheritance l)eing equal to one^ as it should he. Tt is, as you see, the property of this infinite series that each series is equal to the sum of those that follow. Thus an inheritance is not merely dual, but through the parents it is multiple, and the average contributions made by grandparents, great-grandparents, etc., are definite, and diminish in a precise ratio according to the remoteness of the ancestors (Thomson). However true this law may be when applied to the average inheritance of masses of people, it does not apply to individual cases. Galton himself 1‘ecognised this, for he says : Though one half of every child may be said to be derived from either parent, yet he may receive a heritage from a distant progenitor that neither of his parents possessed as personal characteristics.^^ Again, speaking of particulate inheritance, he remarks : All living beings are individuals in one aspect, composite in another. We seem to inherit, bit by bit, this element from one progenitor, that from another, in the pro- cess of transmission by inheritance, elements derived from the same ancestor are apt to appear in large groups, just as if they had clung together in the pre-embryonic stage, as perhaps they did.^^ They form what is well expressed by the word traits —traits of feature and character, that is to say, continuous features, not isolated points. The offspring of parents possess a mosaic of inheritance 'bearing usually a more or less similarity, yet the mosaics of characters, whether bodily or mental, are not in any way identical except in the case of identical twins. Now there is a reason for this. Identical or similar twins are the result of fertilisation of one ovum containing twm germs of identical substance. Before now leaving GaltoiTs law to pass on to a brief description of the Mendelian doctrine let me call attention to his important researches on the history of twins, for probably nothing has shown more conclusively the dominant influence of heredity on character. He found that similar twins living in a different environment nevertheless remained similar in temperament and character, while dissimilar twins brought up and living in the same environ- ment remained dissimilar. These dissimilar twins, however, were the product of two sepai’ate ova. This shows that every germ has a different potentiality and inheritance. Mfc]Ni)KLiAN Doctrine. It is only within the last twelve years that the important researches of Gregor Mendel in the monastery of Brunn have been brought to light and