Nettleship: The Marriage of Kin 



261 



scious selection on the part of some of 

 the authors whose data he quotes, the 

 statistics are not entirely trustworthy, 

 the conclusion is that consanguineous 

 unions have certainly not proved to be 

 less productive than others, and that 

 the probabilities point to their being 

 more so. 



The only contribution I can make at 

 the moment to this subject shows very 

 little difference between the number of 

 children born to parents who were, and 

 were not, cousins respectively. The data 

 relate to the chronic progressive eye- 

 disease, Retinitis pigmentosa; the num- 

 bers are not nearly large enough for 

 final conclusions, and the information 

 on which they are based was sometimes 

 unavoidably incomplete. But I give 

 them for what they are worth. In 

 ninety-three completed families of chil- 

 dren (childships) the offspring of non- 

 consanguineous parentage, containing 

 cases of the disease just mentioned, 

 there were 591 children, or 6.3 to each 

 marriage (average). In forty-eight 

 childships the offspring of consanguine- 

 ous parentage (usually first cousinship) 

 there were 259 children or an average 

 of 5.5 to each marriage. The difference 

 of fertility, such as it is, is against the 

 cousin marriages, but as already stated 

 we could not safely draw conclusions 

 from such a small series, even if it 

 were certain that consanguinity had 

 been recorded in every instance where 

 it had been present. 



I think, therefore, we may conclude 

 that marriages between cousins are as 



safe from the eugenic point of view as 

 any other marriages, provided the 

 parents and stock are sound. 



The difficulty, of course, both for 

 consanguineous and out'-marriages is to 

 decide upon this vital point; and as for 

 obvious reasons the family history is 

 more likely to be forthcoming for a pair 

 of cousins than for an unrelated pair, 

 wc have here a part explanation of the 

 aversion to cousin marriage met with 

 in some families. This explanation will 

 tell with special force if the disease or 

 defect is relatively rare for then it will 

 be more likely to occur, though in a 

 latent form, in two cousins than in two 

 strangers. But if the defect appre- 

 hended be a frequent one, e. g., tuber- 

 culosis, the chances of the hereditary 

 liability to it being present in both 

 parents and intensified in their children 

 may be much the same whether the 

 parents were cousins or not. 



It seems to me that since we as yet 

 know next to nothing of how the 

 various transmissible characters, good, 

 bad or indifferent, are, or at least may 

 be, linked together in inheritance; and 

 that there are many other factors in 

 marriage beyond those relating directly 

 to race improvement or the reverse; it 

 is best, in the present state of our 

 information, not to discourage marriage 

 between cousins unless there be a clear 

 case; e. g., inferiority or instability of a 

 definite kind, or the history in the stock 

 of such distinct diseases, or liabilities 

 to them, as the eye disease. Retinitis 

 pigmentosa, or deaf -mutism and others, 

 more familiar to us, that could be named. 



Pan-American Scientific Congress 



The second Pan-American Scientific Congress will be held in Washington from 

 December 27, 1915, to January 8, 1916. Eugenics has been alloted a place in the 

 section for Anthropology, while plant-breeding and animal-breeding will come 

 under the Section on Conservation of Natural Resources, Agriculture, Irrigation 

 and Forestry. It is hoped that the principal genetists of Central and South America 

 will be in attendance, and will describe the practical work in breeding which is being 

 done in those countries. George M. Rommel, secretary of this Association, is 

 chairman of the subcommittee dealing with conservation and agriculture. 



