An introduction to the study of heredity / by E.W. Macbride.

  • MacBride, E. W. (Ernest William), 1866-1940.
Date:
[1924]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: An introduction to the study of heredity / by E.W. Macbride. Source: Wellcome Collection.

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    population; many thoughtful American citi zens view the continuance of this process with grave apprehension. But in addition to racial differences we have to consider the effects of germ-weakening and the consequent production of “ mutations.” This germ-weakening seems to arise most readily in large towns under conditions which favour overcrowding and unhealthy conditions during conception. Several so-called “ sex- linked ” mutations have already been detected in the human race; amongst them are colour blindness, night-blindness and hsemophilia (inability of the blood to form a clot when it issues from a wound, and hence the tendency of the wounded person to bleed to death); these, however, are not widespread and it cannot be maintained that they do any great amount of social damage; but there is a mutation known as “mental defect” which is of colossal social importance. This mutation consists in the inability of the mind to expand and develop its powers as the body grows. £ It exists in a great variety of grades of intensity, and on being crossed with the type, behaves as a recessive. The various grades are distinguished from one another by the age at which a normal child acquires an