Heredity : a study with special reference to disease / by R.A. Douglas Lithgow.

  • Robert Alexander Douglas-Lithgow
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Heredity : a study with special reference to disease / by R.A. Douglas Lithgow. Source: Wellcome Collection.

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    i8 type is subject to the law of heredity no less than the specific type.” It must, however, be remembered that an exact likeness, either physical, mental, or moral, is never transmitted by inheritance; neither an exact likeness of either parent, nor an exact composite of both. All breeders of stock know very well that if they wish to develop and perpetuate certain qualities in the offspring, they must exercise the greatest care in the selection of the parents; and human beings, however well-informed, are far too prone to forget that similar laws are still more applicable to themselves. The fact is, that as the law of inheritance of like qualities in the lower animals manifests itself in simpler and less complex channels than in the human species ; so, also, it is less largely modified in the former than in the latter by laws of variation. As Dr. Maudsley says :—“ There is always a principle of variation at work in breeding, contesting the ground, as it were, with a principle of heredity, the effects of which are so great sometimes that resemblances are hidden or overborne entirely. Now, as the human body is the most complex organic substance in the world—' the most compounded mass in nature,’ as Bacon calls it—it affords infinite scope for modifications, neutralisations, and variations of qualities; and the reasons are obvious why we cannot predict results. Countless variations may occur in each case. . . . Most of these variations die with the individual; but some of them, meeting with fit surroundings, and being fostered thereby, are propagated from one generation to another, and become fixed qualities of the family stock. For the qualities of the stock are deeper and more stable than those of the individual, and the qualities of the species deeper and more stable than those of the family. The law of heredity is most evident in
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