Licence: Public Domain Mark
Credit: The intermarriage of relatives and its consequences. Source: Wellcome Collection.
Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.
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![have come under observation [as the results of intermarriage]. Cases II., III., and IV., illustrate the combination of mental and physical defects, and afford an interesting manifestation of sterility. In Case V., we have idiocy, imbecility, deaf-dumbness, and lameness, combined with a large infant mortality.” The “ Cases ” given above are manifestly “ selected,” and any general conclusion drawn from them .would be unfair and indefensible. But there are two methods of inquiry by ' either of which the suspicion of “selected” cases, and the logical invalidity of the inferences deduced from “selected” cases, may be dissipated. The first would take the form of fixing upon some one mental or physical disease in a district of sufficiently extensive dimensions, and then ascertaining the relative number of marriages of consanguinity and of non- consanguinity in which that specific disease exhibited itself. If the ratio of its appearances in cousin marriages was found to be distinctly and notably greater than that in marriages in which no relationship could be traced, the inference would be inevitable that intermarriage was responsible for the dis- proportion. The second method would consist in selecting some localities of large area, ascertaining the family history of every marriage in those localities, and comparing the results of those marriages in which kinship existed with those in which it did not exist. The refusal of the public authorities to register marriages of consanguinity, as such, makes it impossible to obtain a strictly and mathematically exact return by either method; but the enterprise of individuals, who have laudably taken advantage of the opportunities placed in their way, enables us to establish with practical accuracy that marriages of consan- guinity are, as a rule, attended with lamentable consequences. As a postulate, however, to the deducing of fair and legi- timate inferences from the statistics I am about to give, it must be continuously borne in memory that the marriages of blood-relatives are comparatively few. Dr. Howe, of Massa- ! chusetts—one of the best known of modern scientists— speaking of marriages of first cousins, says that “ they are not even perhaps as one to a thousand to the marriages of persons not so related.” This estimate is quoted, and](https://iiif.wellcomecollection.org/image/b24761710_0009.jp2/full/800%2C/0/default.jpg)
