On the other hand, breeders of animals tell us that a single drop of new blood (or rather sperm) is enough to counteract all the evil effects of consanguinity. In man the most frequent incests are always interrupted by some other union. The Ptolemies, who nearly always married their sisters, nieces or cousins, lived long and were far from being sterile. In Ceylon, the Weddas perpetuate their consanguineous unions; insanity is rare among them, but they are small, unfruitful and tend to become extinct. In Europe, the question of marriages between first cousins has been much discussed, and it has been constantly attempted to prove that they are injurious. Nevertheless, when we examine the question impartially, we always find that the prejudices against them do not arrive from consanguinity, but from certain pathological defects, such as insanity, hemophilia, etc., which are naturally perpetuated by consanguineous unions when they are accumulated in one family, as well as when two insane persons of different families marry. Therefore it is not consanguineous unions in themselves (which are always accidental in man and interrupted by others) but the hereditary reproduction of pathological defects, often of blastophthoric origin, which are the real cause of the evil. Statistics have clearly proved that marriage between first cousins plays no part in the causes of insanity. Influenced, no doubt, by general opinion, Westermark tries to believe in some instinctive repulsion of man for consanguineous unions. If in modern society such unions, perpetuated between parents and children, brothers and sisters, were still produced as in animals I should agree that they might be injurious to the species; but, considering how cosmopolitan and mixed is our modern society, I cannot make the concession. On the contrary, I maintain that the isolated unions which still take place between relatives in civilized countries are so exceptional that they do not present the least danger, excepting among the families of degenerates. It is therefore only a question of superstition. What we have to guard against are unions between pathological individuals and blastophthoric influences. We must not forget that many degenerates and idiots have a great pathological tendency to incest, and this is no doubt why the effect has been confounded with the cause.