Dr. Barr finds 49 out of 4050 cases of idiocy or 1.21 per cent, in which there was a family history of consanguinity.  This is little higher than the average frequency of first cousin marriage, and an analysis of 41 of these cases does not show one case that can be attributed to consanguinity alone.  To quote:  “Two were the result of incestuous connection—­one of brother and sister, the other of father and daughter, and in the others there was an undoubted history, of grave neuroses."[64] “Beach and Shuttleworth find in the consideration of their 100 cases (out of 2,380 idiots), giving 4.2 per cent (of consanguineous parentage) that the bad effects are due rather to the intensification of bad heredity common to both parents."[65]

[Footnote 64:  Barr, op. cit., p. 94.]

[Footnote 65:  Ibid., p. 109.]

Dr. Arthur Mitchell examined all idiots in nine counties of Scotland and found that 42 out of 519 or 8.1 per cent of whom the parentage was known, were children of first cousins.[66] Dr. Down found 46 out of 852 or 5.4 per cent to be children of first cousins.[67] Dr. Grabham of the Earlswood Idiot Asylum in Surrey, England, stated that 53 out of 1388 patients were the offspring of first cousins.  The facts, he adds, were obtained from the parents and are “therefore tolerably trustworthy."[68] Other investigations give percentages as follows:  Kerlin, 7; Rogers, 3.6; Brown, 3.5 and C.T.  Wilbur, 0.3.[69]

[Footnote 66:  Darwin, see Jour.  Stat.  Soc., p. 173.]

[Footnote 67:  Huth, Marriage of Near Kin, pp. 210-211.]

[Footnote 68:  Darwin, op. cit., p. 166.]

[Footnote 69:  Barr, op. cit., p. 109.]

The earlier American writers, Drs. Howe and Bemiss, believed that consanguinity was a cause of idiocy.  Dr. Howe inquired into the parentage of 359 idiots and found that in 17 families the parents were nearly related; in one of these cases there were 5 idiotic children; in 5 families there were 4 idiots each; in 3 families 3 each; in 2 families 2 each; and in 6 families i each.  In all 17 families there were 95 children of whom 44 were idiots, 12 were scrofulous and puny, 1 was deaf, 1 dwarf—­58 in low health or defective, and only 37 fairly healthy.  These of course are selected cases and do not indicate at all, as Dr. Howe supposed, that consanguinity was the cause of the disasters.  He adds that in each case one or both of the parents were either intemperate or scrofulous, and that there were also other predisposing causes.[70] Dr. Bemiss found that 7.8 per cent of his 3942 children of consanguineous marriages were idiots, while but 0.7 per cent of the children of non-consanguineous parentage were idiotic.[71] A more detailed examination reveals the fact that in a large number of these, one or both of the parents were mentally defective.  For example, in a marriage of double cousins the wife was “feeble minded” and the six children were of inferior mentality.  In a case of first-cousin