Full text: Problems in eugenics

F. W. Mott.Medicine and Eugenics.401 
recognised, however, that this law only applied to masses of people and not 
to individual cases, for he says : “ Though one half of each 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 char­ 
acteristics.” 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 process 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 character, 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 twins are the result of fertilization of 
one ovum containing two germs of identical substance, and this leads rne 
to refer to Galton’s remarkable inquiry into the History of Twins in con­ 
nection with Nature and Nurture. 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 separate ova with dissimilar germs. This shows that every germ has 
a specific energy of its own, as manifested by a different potential 
inheritance. Galton also made a statistical inquiry into good and bad tempers, and 
as a result of this inquiry he says : “It now becomes clear enough and 
may be taken for granted that the tempers of progenitors do not readily 
blend in the offspring, but that some of the children take mainly after one 
of them, some after another, but with a few threads, as it were, of 
various ancestral tempers woven in, which occasionally manifest themselves. 
If no other influences intervened, the tempers in the children of the same 
family would on this account be almost as varied as those of their ancestors. 
To recapitulate briefly, one set of influences tends to mix good and bad 
tempers in a family at haphazard; another tends to assimilate them, or 
that they shall all be good or all be bad; a third set tends to divide each 
family into contracted portions. These facts, ascertained by Galton, are. 
of great interest in connexion with the inheritance of the predisposition to 
nervous and mental diseases, a predisposition which is termed the neuro­ 
pathic taint. Galton’s law of filial regression again seems to explain 
many facts regarding the inheritance of feeble-mindedness as well as ability. 
In respect to the latter, Galton showed that only a few out of many children 
would be likely to differ from mediocrity as their mid parent, and still 
fewer would differ as widely as the more exceptional of the two parents. DD

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