With the exception of this case, the closest kind of intermarriage which we have opportunities of studying is that between first cousins. Unfortunately, the observations hitherto made on the subject are far from decisive. Several writers, as M. Périer, Dr. Voisin, and Mr. Huth, believe that there are no injurious results at all from those marriages, unless the parents are afflicted with the same hereditary morbid tendencies,[2002] whilst others, as M. Devay and M. Boudin, express the most alarming opinions as to the bad effects of consanguineous marriages. Such alliances are supposed to bring evils of many different kinds upon a population, as sterility, idiocy, epilepsy, insanity, deaf-muteism, congenital malformations in the offspring, cretinism, albinoism,[2003] &c. But how little the statements of the various writers agree with each other appears, for instance, from the fact that M. Boudin found the proportion of deaf-mutes born in consanguineous marriages, in the Imperial Institution of Deaf-Mutes at Paris, to be 28·35 per cent., whereas, according to Dr. Mitchell, it amounts to 5·17 per cent. in Scotch and English institutions.[2004] As it is impossible to dwell here upon the investigations of the several writers, of which Mr. Huth has given so complete an account, I shall confine myself to a statement of the general results attained by those investigators who have founded their inquiries on a more trustworthy statistical basis. Adopting a method different from that of his predecessors, Professor G. H. Darwin has endeavoured first to discover the proportion of consanguineous marriages in the whole population, and then to find out whether the offspring of those marriages exhibit a greater percentage of individuals, defective in one way or another, than the offspring of non-consanguineous marriages. His investigations tend decidedly to invalidate the exaggerated conclusions of many previous writers, but he thinks that “there are nevertheless grounds for asserting that various maladies take an easy hold of the offspring of consanguineous marriages.”[2005] He did not find evidence that the marriage of first cousins had any effect in the production of infertility, deaf-muteism, insanity, or idiocy, but he observed a slightly lowered vitality amongst the offspring of first cousins, and a somewhat higher death-rate than amongst the families of non-consanguineous marriages.[2006] Moreover, the numbers of boating men belonging to the twenty boats at Oxford and thirty at Cambridge, in the first and second division, and those of selected athletes from some schools in England, justified, to some extent, the belief “that offspring of first cousins are deficient physically, whilst at the same time they negative the views of alarmist writers on the subject.”[2007] It is curious that, in spite of such unambiguous statements, Mr. Darwin’s paper has generally been quoted as an evidence of the perfect harmlessness of first cousin marriages.