M. Stieda has found that, in the departments of France, the number of bodily or mentally infirm people increases almost constantly in proportion to the number of consanguineous marriages, as will be seen from the following table:— Number of Number of consanguineous Number of Group. departments. marriages in infirm people in each thousand each thousand marriages. inhabitants. I. 10 5·4 2·3 II. 10 8·3 2·8 III. 14 9·95 3 IV. 10 11·2 2·4 V. 13 12·5 2·8 VI. 8 13·8 3 VII. 14 15·8 3·5 VIII. 10 19·2 3·25 —————————————————————————————————-———————————-———————————-—————-— I.—IV. 44 9·2 2·65 V.—VIII. 45 14·8 3·1[2008] The Danish physician, Dr. Mygge, published in 1879 a book on ‘Marriage between Blood-Relations,’ which unfortunately has received much less attention than it deserves.[2009] Thanks to the trustworthiness of the method, the number of cases considered, and the author’s impartiality, it is probably the most important statistical contribution hitherto issued on this subject. Dr. Mygge found, from the information he received from various parts of Denmark, that in that country, or at least in the parishes of it which came under his observation, there occur, among the children of related persons, comparatively more idiots, lunatics, epileptics, and deaf-mutes than among others. He considers it probable, too, though not proved, that such children die in a higher ratio and are more liable to certain diseases. But, on the other hand, he did not notice any perceptible difference in fertility between consanguineous and crossed marriages.[2010] In these inquiries, Dr. Mygge followed the method applied by the Norwegian physician Ludvig Dahl twenty years earlier. Through careful investigation of 246 marriages, eighty-five of which were between first cousins and four between still nearer relations, this inquirer was led to the conclusions that consanguineous marriages are somewhat less fertile than crossed marriages; that they produce comparatively many more still-born and sickly children; and that insanity, idiocy, deaf-dumbness, and epilepsy occur about eleven times as often among the offspring of relations, as among the offspring of unrelated parents. But he admitted that the numbers compared were too small to make his conclusions decisive.[2011]