A contribution of interest on the above subject appears in a recent Thèse de Paris (1900) by Dr. Theophile Gillet of Paris, dealing with the results of consanguineous marriages in relation to certain neuroses and psychoses. Dr. Rilliet and Dr. Barthez in their classical “Treatise on the Diseases of Children” (1859) had stated that the results of consanguinity of parents were as follows. First, fewer births; secondly, more miscarriages and still births than the average; thirdly, weakness (physical and moral) of the surviving children; fourthly, a special tendency in the offspring to diseases of the nervous system, such as epilepsy, idiocy and imbecility, deaf-mutism, and local cerebral palsies; and lastly, a special proclivity in the offspring to tuberculous degeneracy. It has since been stated that among the more frequent results of consanguinity in the parents are such abnormalities as albinism, deaf-mutism, and retinitis pigmentosa in the offspring, even in cases where but one parent showed the specific morbid taint. The observations of Dr. Gillet were made at the Bicêtre during 11 years (from 1889 to 1900), during which period 1228 children were under care and treatment. Inquiries were also made into the histories of 425 girl patients at the Fondation Vallée, Paris, an institution for children suffering from nervous diseases. The total number of cases investigated was, therefore, 1653. Inquiries into the family histories of these patients elicited the fact that there were 45 instances of consanguineous marriage in the parents. These 45 families were minutely studied, with the result that the offspring of these families taken en bloc showed 19 cases of idiocy, 14 of epilepsy (idiopathic or symptomatic), eight of imbecility, three of hydrocephalus, one of chorea, and one of idiocy [sic], a total of 46 grave neurouses and cerebral defects. The relative degrees of consanguinity were as follows. In 28 instances the father and mother were first cousins, in nine they were the children of first cousins, in seven instances they were cousins of the third, fourth, and fifth degree, and in one case uncle and niece. Inquiry into the condition of their children during infancy revealed the fact that convulsions and meningitis were notably prevalent, while idiocy or imbecility and chorea were also found to prevail in an abnormally high degree. Taking the total of all the surviving children of these consanguineous marriages it appeared that 2.7 per cent of them suffered from idiocy, epilepsy, imbecility, hysteria, or other grave cerebral disorders - a proportion very much larger than that generally present among the offspring of those in the same rank of life but who had not contracted consanguineous marriages.