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.
There is no really great scientist in biology at the present moment who teaches the hereditary transmission of acquired characteristics. Modifications of the organism that become matter for heredity have existed for many generations and we cannot tell just how they began. There is no doubt that there is some hereditary influence, for insanity in the same family is likely to keep recurring in successive generations. More than this, affections of certain less important organs are evidently a common trait in certain family strains. There is no doubt that in some families stomach affections are the rule in successive generations. It is very hard to say, however, just when such defective organisation became a family trait. The tendency to nervous affections is undoubtedly a similar family affair. Certain affections have been hereditary traits for many generations. An excellent example of this is the so-called Huntingdon's chorea, which several generations of American doctors, of the name of Huntingdon, by following carefully the history of certain families on Long Island, succeeded in tracing through four generations.
The habits of life of a father or a grandfather may so weaken the physical constitution of his descendants as to make them less capable of resisting infections in the physical order, or in the moral order of withstanding trials and temptations, and the allurement to abuse of nervous excitement to which they may be subjected. That some acquired pathological condition, however, as stomach trouble, or heart [{123}] trouble, or affection of the liver or of the brain, should be directly transmitted, is quite as nonsensical as that the loss of an arm should be a subject for hereditary transmission. On investigation it will be found that the pathological conditions of immediate ancestors are themselves only a manifestation of family traits that have existed for many generations. The possibility of inheritance must therefore always be borne in mind. We are utterly unable as yet to understand how such family traits are originally developed, since, in ordinary experience, at least, acquired characteristics are not the subject of inheritance or transmission, and consequently it becomes difficult to understand how they ever became impressed upon the family constitution.
Notwithstanding this general principle with regard to heredity, there are a number of striking observations which show that even unimportant peculiarities may occur from generation to generation, though it is not always easy to decide where the peculiarity originated. The well-known example of the occurrence of six toes has already been mentioned, and is an oft-quoted bit of evidence as regards hereditary transmission. An extra finger on the hand, or some portion of an extra finger, at least, comes in the same category. Not long since it was pointed out that harelip is another of these peculiarities that readily lends itself to hereditary transmission. Recently there was the report of a family into which there were born four girls with harelip and cleft palate, and three boys not showing any trace of these deformities.
Often when in such cases there is no definite history of harelip, it is found that in either one of the parents there is a very high arched palate and a thin upper lip, showing that the normal occlusion of the cleft which exists here during foetal development is not quite perfect, and this peculiarity may be traced for several generations back, with an occasional occurrence of harelip as an exaggerated example of the faulty tendency not to produce sufficient tissue in this neighbourhood for the proper closure of the embryonic cleft.
An even more striking manifestation of a physical anomaly, as a family trait, is the condition known as hemophilia. This [{124}] tendency to bleed easily, so that a slight scratch, or the pulling of a tooth, may give rise to fatal hemorrhage, occurs, as a rule, only in males, but is transmitted through the female line. It is in the mother's male relatives that the history of its previous occurrence is found, and the tendency usually can be traced through several generations, until it is lost in vague tradition. It is no wonder, with such examples before them as six-toedness, harelip, and hemophilia, that physicians have been ready to accept heredity of qualities in the moral order, traits of character and disposition, and pathological tendencies to crime or passion or indulgence.
One of the most frequently discussed conditions of supposed pathological inheritance of this order is dipsomania. Everyone has heard it said, "Poor fellow, how can he help it; his father was a drunkard before him." As we have already said, in such direct cases inheritance is absolutely unproven. An alcoholic father may transmit a very weak physical constitution to his children, and this may prove inadequate to enable them to withstand the emotional strain and worry of modern great city life, and, as a consequence, they may take to alcohol for consolation until the habit is formed, and then the craving for stimulants supplies the place of any hereditary influence that may be supposed to be needed.
Of course there are cases of the drink habit in which, after a number of generations of family history of alcoholism, an individual seems to have the craving for stimulants born in him. In such cases it is not unusual to find that the patient, for such he must be considered, is able to avoid indulgence in liquor entirely, except at certain times. Every physician of any large experience has had under his care dipsomaniacs who had no difficulty in keeping away from liquor for weeks, or even months, but who had regularly recurring periods, sometimes as far apart as every three months, when they had an irresistible craving for stimulants come over them. The regularity of the interval in these cases is often very remarkable. Here, of course, we may be in the presence of some as yet not well-understood periodical law of cell life, with consequent depression, and then the irresistible craving for stimulation. [{125}] As a rule, however, it would seem that in most of these cases suggestion has great influence. As we have said elsewhere, with regard to suicide, when a man has constantly before his mind's eye the fact that a father, perhaps a grandfather, or other members of the family, have committed suicide, he is likely to be much more easily led to the thought of this way of escaping hard conditions in life than are other individuals. The man who knows that the fact that his father indulged too freely in stimulants will be looked upon by many as an excuse for his deviations in this matter is likely to be more easily led to take an occasional drink at moments of depression, or for friendship's sake, though he realises that it so weakens his will power over himself that he is likely to take too much before he stops.
The passage in Julius Caesar (Act. I. sc. 2) in which Cassius says: