HEREDITARINESS. The influence exerted by parents on the qualities of their off spring is universally admitted, but the relative amount of influence which each parent exerts is still to sonic extent an open question.
The general structure of the body, the height, the degree of development of the bones and muscles, the tendency to obesity or leanness, etc., seem to depend as fre quently on one parent as on the other, in the case of man; but in many animals, as the dog, horse, etc., the father most frequently determines the general form and the size of the body.
The color and complexion of the offspring follow no definite rule. Sometimes the colors of the two parents appear undiluted in the offspring, as in the case of a piebald colt, resulting from the union of a bay stallion and a white mare, while in other cases an intermediate tint appears in the young. In the offspring resulting from the union of individuals of the dark and white human races, we have this intermediate tint devel oped; but it is belieVed that the color of the father usually predominates over that of the mother.
A very curious department of this subject is the transmission to the offspring of special marks or deformities exhibited by one of the parents or more remote ancestors, and not common to the species. nevus (or mother's marks), moles, harelip, growths of hair in unusual places, an unusual number of fingers or toes, and special malforma tions of the heart and of other organs, have been frequently traced to hereditary influ ence. It is deserving of remark that these peculiarities have a tendency to show them selves in alternate,gencrations, or even at greater intervals. Burdach, Blumenbach, and other eminent physiologists, have held the doctrine. that parents (whether dogs or men) who have suffered accidental or intentional mutilation of certain parts (as, for example, the tail, etc.,) often produce offspring which inherit these injuries; for instance, the dogs with cropped tails often produce pups with cropped tails. If the facts are true (which possibly may be doubtful), the results are probably due to an impression on the mother's mind rather than to an hereditary tendency. The immemorial practice of
the Chinese in stunting the feet of their women has not produced a natural variety with that peculiarity.
Morell, in his Introduction to Mental Philosophy, observes that there are latent powers or tendencies which have been and which often remain unknown until brought out by peculiar circumstances. He gives the familiar example of the pointer. The habit of pointing at game is originally an acquired one; but so strongly does this habit become seated in the race, that the very first time the young pointer is taken into the field, he will stand and mark it, thus developing a purely hereditary instinct. "Exactly in the same way," he adds, " we find in man peculiarities of mind, temper, thought, habit, volition, etc., appearing and in families and races. Lord Brougham found some of his grandfather's writing. exactly resembling his own [which is very peculiar], though the grandfather had died before he was born, and his father's was quite different." It is alleged that the children of skilled artisans are, as a rule, more apt at petty manipulation than the children of ordinary laborers, and that hence the population of certain towns—Birmingham, for example—has a great advantage over that of other towns in point of manufacturing industry.
It is well known that longevity or the reverse, a tendency to great fruitfulness or to sterility, peculiarities in the degree of delicacy in the external senses, and a special tendency to certain diseases—as gout, pulmonary consumption, cancer, etc.—are transmitted in descent from one or other parent to the. offspring. The predisposition to any certain special disease may be transmitted by either parent; but where both parents have been affected, the offspring are especially liable to suffer from it. Deformities and diseases, also, engendered by circumstances to which the exposure is lifelong, or affecting successive generations, are more certainly and con spicuously hereditary.