Some families are remarkable during long periods for tall and handsome figures and striking regularity of features, while in others a less perfect form, or some peculiar deformity reappears with equal constancy. A family in Yorkshire is known for several generations to have been furnished with six fingers and toes. A family possessing the same peculiarity resides in the valley of the Kennebec, and the same has reappeared in one or more other families connected with it by marriage.
The thick upper lip of the imperial house of Austria, introduced by the marriage of the Emperor Maximillian with Mary of Burgundy, has been a marked feature in that family for hundreds of years, and is, visible in their descendants to this day. Equally noticeable is the "Bourbon nose" in the former reigning family of France. All the Barons de Vessins had a peculiar mark between their shoulders, and it is said that by means of it a posthumous son of a late Baron de Vessins was discovered in a London shoemaker's apprentice. Haller cites the case of a family where an external tumor was transmitted from father to son which always swelled when the atmosphere was moist.
A remarkable example of a singular organic peculiarity and of its transmission to descendants, is furnished in the case of the English family of "Porcupine men," so called from having all the body except the head and face, and the soles and palms, covered with hard dark-colored excrescences of a horny nature. The first of these was Edward Lambert, born in Suffolk in 1718, and exhibited before the Royal Society when fourteen years of age. The other children of his parents were naturally formed; and Edward, aside from this peculiarity, was good looking and enjoyed good health. He afterward had six children, all of whom inherited the same formation, as did also several grand-children.
Numerous instances are on record tending to show that even accidents do sometimes, although not usually, become hereditary. Blumenbach mentions the case of a man whose little finger was crushed and twisted by an accident to his right hand. His sons inherited right hands with the little finger distorted. A bitch had her hinder parts paralyzed for some days by a blow. Six of her seven pups were deformed, or so weak in their hinder parts that they were drowned as useless. A pregnant cat got her tail injured; in each of her five kittens the tail was distorted, and had an enlargement or knob near the end of each. Horses marked during successive generations with red-hot irons in the same place, transmit visible traces of such marks to their colts.
Very curious are the facts which go to show that acquired habits sometimes become hereditary. Pritchard, in his "Natural History of Man," says that the horses bred on the table lands of the Cordilleras "are carefully taught a peculiar pace which is a sort of running amble;" that after a few generations this pace becomes a natural one; young untrained horses adopting it without compulsion. But a still more curious fact is, that if these domesticated stallions breed with mares of the wild herd, which abound in the surrounding plains, they "become the sires of a race in which the ambling pace is natural and requires no teaching."
Mr. T.A. Knight, in a paper read before the Royal Society, says, "the hereditary propensities of the offspring of Norwegian ponies, whether full or half-bred, are very singular. Their ancestors have been in the habit of obeying the voice of their riders and not the bridle; and horse-breakers complain that it is impossible to produce this last habit in the young colts. They are, however, exceedingly docile and obedient when they understand the commands of their masters."
A late writer in one of the foreign journals, says that he had a "pup taken from its mother at six weeks old, who although never taught to 'beg' (an accomplishment his mother had been taught) spontaneously took to begging for every thing he wanted when about seven or eight months old; he would beg for food, beg to be let out of the room, and one day was found opposite a rabbit hutch apparently begging the rabbits to come and play."
If even in such minute particulars as these, hereditary transmission may be distinctly seen, it becomes the breeder to look closely to the "like" which he wishes to see reproduced. Judicious selection is indispensable to success in breeding, and this should have regard to every particular—general appearance, length of limb, shape of carcass, development of chest; if in cattle, the size, shape and position of udder, thickness of skin, "touch," length and texture of hair, docility, &c., &c.; if in horses, their adaptation to any special excellence depending on form, or temperament, or nervous energy.
Not only should care be taken to avoid structural defects, but especially to secure freedom from hereditary diseases, as both defects and diseases appear to be more easily transmissible than desirable qualities. There is often no obvious peculiarity of structure, or appearance, indicating the possession of diseases or defects which are transmissible, and so, special care and continued acquaintance are necessary in order to be assured of their absence in breeding animals; but such a tendency although invisible or inappreciable to cursory observation, must still, judging from its effects, have as real and certain an existence, as any peculiarity of form or color.
Every one who believes that a disease may be hereditary at all, must admit that certain individuals possess certain tendencies which render them especially liable to certain diseases, as consumption or scrofula; yet it is not easy to say precisely in what this predisposition consists. It seems probable, however, that it may be due either to some want of harmony between different organs, some faulty formation or combination of parts, or to some peculiar physical or chemical condition of the blood or tissues; and that this altered state, constituting the inherent congenital tendency to the disease, is duly transmitted from parent to offspring like any other quality more readily apparent to observation.