their effects upon society, and more particularly their bearing upon American social evolution. The problems to be considered are not only those which relate primarily to the individual and secondarily to the race, such as the supposed effect of blood relationship in the parents upon the health and condition of the offspring; but also the effect, if any, which such marriages have upon the birth-rate, upon the proportion of the sexes at birth, and the most fundamental problem of all, the relative frequency with which consanguineous marriages take place in a given community.

No thorough and systematic study of the subject has ever been made, and could not be made except through the agency of the census. The statistical material here brought together is fragmentary and not entirely satisfactory, but it is sufficient upon which to base some generalizations of scientific value. The sources of these data are largely American. Little attempt is made to study European material, or to discuss phases of the problem which are only of local concern. Some topics, therefore, which have frequently been treated in connection with the general subject of consanguineous marriages are here ignored as having no scientific interest, as for instance that of the so-called "marriages of affinity," which has been so warmly debated for the past fifty years in the British Parliament.

For obvious reasons it will often be impossible to distinguish between the different degrees of consanguinity, but wherever possible the degree will be specified. It is probable that where a number of marriages are vaguely given as consanguineous, few are more distant than second cousins, for in the United States especially, distant relationships are rarely traced except by genealogists. In designating degrees of relationship the common terminology will be used, as in the following table, expressing, however, the rather clumsy expression, "first cousin once removed" by the simpler form "1-1/2 cousin."

By far the greater part of the literature of consanguineous marriage is of a controversial rather than of a scientific nature, and a search for statistical evidence for either side of the discussion reveals surprisingly little that is worthy of the name. Yet men of high scientific standing have repeatedly made most dogmatic assertions in regard to the results of such unions, and have apparently assumed that no proof was necessary. For example, Sir Henry Sumner Maine "cannot see why the men who discovered the use of fire, and selected the wild forms of certain animals for domestication and of vegetables for cultivation, should not find out that children of unsound constitution were born of nearly related parents."^[2]

Much space is given to the alleged "innate horror of incest," and frequent appeals are made to Scripture, wrongly assuming that the marriage of cousins is prohibited in the Mosaic Law.

The origin of "prohibited degrees" is only conjectural. The Christian Church apparently borrowed its prohibitory canons from the Roman Law,^[3] and a dispensation is still necessary before a Catholic can marry his first cousin. However, such dispensations have always been easy to obtain, especially by royal families, and even the marriage of uncle and niece sometimes occurs, as among the Spanish Habsburgs, and as recently as 1889 in the House of Savoy.

The prohibition of the marriage of first cousins was removed in England by the Marriage Act of 1540,^[4] but by this time the idea of the harmfulness of kinship marriage was so thoroughly impressed upon the people that they were very prone to look askance at such unions, and if they were followed by any defective progeny, the fact would be noted, and looked upon as a chastisement visited upon the parents for their sin. Naturally the idea became proverbial, and in some places it has influenced the civil law.

Perhaps the first printed discussion of the subject in America is from the pen of Noah Webster, in an essay which should be as interesting to the spelling reformer as to the sociologist.^[5] He writes: "It iz no crime for brothers and sisters to intermarry, except the fatal consequences to society; for were it generally practised, men would become a race of pigmies. It iz no crime for brothers' and sisters' children to intermarry, and this iz often practised; but such near blood connections often produce imperfect children. The common peeple hav hence drawn an argument to proov such connections criminal; considering weakness, sickness and deformity in the offspring az judgements upon the parents. Superstition iz often awake when reezon iz asleep."

From about 1855 to 1880 much was written about the effect of consanguineal interbreeding. One of the first contributions came from America. In 1858 Dr. S.M. Bemiss, of Louisville, Kentucky, reported to the American Medical Association the results of his investigation of 833 cases of consanguineous marriage.^[6] His compilation remains to this day the largest single piece of direct statistical work on the subject. Unfortunately, however, his statistics have a strong, if unintentional, bias which seriously affects their value. In France one of the earliest discussions was by M. Boudin,^[7] who evidently obtained the Bemiss report (attributing it to Dr. O.W. Morris, who had quoted freely from Bemiss),^[8] and enlarged greatly upon its fallacies. He also collected statistics of the deaf-mutes in Paris, and, by an amazing manipulation of figures, "demonstrated" that consanguinity of the parents was the cause of nearly one-third of the cases of congenital deafness. The savants of the Société d'Anthropologie took sides and the debate became very entertaining. Finally M. Dally came to the rescue, and published some very sane and logical articles which avoided both extremes, and first advanced the theory that any ill effects of consanguineous marriage should be attributed to the intensification of inherited characteristics.^[9]

In England similar discussions took place during the same period, complicated, however, by the presence of the patient and long-suffering "deceased wife's sister." The best of the English work has been the statistical study by George H. Darwin,