Until within a very few years it was considered a matter of common experience and observation that under some circumstances, at least, acquired characteristics were transmitted by heredity. That is to say, it has been definitely asserted as probable, and by many even intelligent people considered absolutely certain, that modifications of a living being undergone during the course of its existence might influence the progeny of that being in various but very definite ways. It was not, of course, thought that if a man lost an arm and subsequently begot a child, the child would be born without an arm, but slighter modifications of the organism were somehow supposed to be transmissible; and, on the other hand, modifications which affect important organic structures of the body were somehow thought to have a definite effect, by transmission, upon corresponding portions of the progeny. When this theory is stated thus baldly, very few people confess their belief in it, yet how many there are who find ample justification for such expressions as, "His father suffered from rheumatism and it is not surprising then that he should have it"; "Her mother had heart trouble and we've always been afraid she would suffer in the same way." We are only just beginning to get beyond the period in which consumption was thought to be directly and almost inevitably inherited. With regard to mental ailments this was frankly conceded by nearly every one. If the direct ancestry suffered from mental disease of some kind, then it is not considered surprising that the immediate descendants should be mentally affected in some way. Physicians are quite as prone as those without medical training to make loose statements of this kind. Of course there is a reason for the confusion that exists in this matter. Oliver Wendell Holmes once said that he could cure any patient that came to him for treatment, if he but applied to him in time. For proper success, however, he considered that many of his patients would have had to come to him in the persons of their great grandfathers. As {122} a matter of fact, many of the supposed hereditary influences that are traced only to a father or a mother are family conditions that have existed many generations, and that were probably originally acquired, but the moment of whose acquisition cannot be definitely determined. We know that the Hapsburg lip has been a distinguishing feature, a persistently recurring peculiarity, in some of the members of the Austrian ruling family in nearly every generation for seven centuries. How much farther back than that it goes we have no way of determining. It is a family affair, a characteristic which became a matter of heredity perhaps ten centuries ago, but the mode of its original acquisition is a mystery.