"The Inheritance of Mental Traits," from Evolution and Genetics, by Thomas H. Morgan, an early criticism of eugenics in an important text (2)

1919. 202 Evolution and Genetics cause, the effects may be to a large extent communicated rather than inherited. It is quite possible of course that an inherited defective dominant character might furnish the starting point for these histories, but that the subsequent events are all due to "bad blood" or "defective germ-plasm" remains to be shown. "Insanity" is another "psychological trait" that is said to be inherited and the numerous pedigrees that have been collected showing that certain types of insanity occur more frequently in certain families than in others seem to furnish evidence in support of such a claim. That is particularly the case in Huntington's chorea ([italics]fig.[end italics] 77) a type of insanity, often leading ultimately to suicide, that does not appear as a rule until middle life or later. Since it appears to be dominant, its history is more easily followed than in most other cases where the dominance or recessiveness is in question. Huntington's chorea has been traced in a limited group of indi- [figure 77 - pedigree chart middle of page] [caption under chart]Fig. 77. - Chart showing the inheritance of Huntington's chorea. ([italics]After Davenport.[end italics]) [end]