Consumption,—that dread foe of modern life,—is the most frequently encountered of all affections as the result of inherited predisposition. Indeed some of the most eminent physicians have believed it is never produced in any other way. Heart disease, disease of the throat, excessive obesity, affections of the skin, asthma, disorders of the brain and nervous system, gout, rheumatism, and cancer, are all hereditary. A tendency to bleed frequently, profusely and uncontrollably, from trifling wounds, is often met with as a family affection.
The inheritance of diseased conditions is also influenced by the sex. A parent may transmit disease exclusively to children of the same sex, or exclusively to those of the opposite sex. Thus, a horn-like projection on the skin peculiar to the Lambert family was transmitted from the father to his sons and grandsons alone. So mothers have through several generations transmitted to their daughters alone supernumerary fingers, color-blindness, and other deformities and diseases. As a general rule, any disease acquired during the life of either parent, strongly tends to be inherited by the offspring of the same sex rather than the opposite. We have spoken of the apparently reverse tendency in regard to the transmission of genius and talent.
ARE MUTILATIONS INHERITABLE?
How, it may be inquired, is it in regard to the inheritance of parts mutilated and altered by injuries and disease during the life of either parent? In some cases mutilations have been practised for many generations, without any inherited result. Different races of men have knocked out their upper teeth, cut off the joints of their fingers, made immense holes through their ears and nostrils, and deep gashes in various parts of their bodies, and yet there is no reason for supposing that these mutilations have been inherited. The Comprachicos, a hideous and strange association of men and women, existed in the seventeenth century, whose business it was to buy children and make of them monsters. Victor Hugo, in a recent work, has graphically told how they took a face and made of it a snout, how they bent down growth, kneaded the physiognomy, distorted the eyes, and in other ways disfigured 'the human form divine,' in order to make fantastic playthings for the amusement of the noble-born. But history does not state that these deformities were inherited; certainly no race of monsters has resulted. The pits from small-pox are not inherited, though many successive generations must have been thus pitted by that disease before the beneficent discovery of the immortal Jenner. Children born with scars left by pustules have had small-pox in the womb, acquired through the system of the mother. On the other hand, the lower animals, cats, dogs, and horses, which have had their tails and legs artificially altered or injured, have produced offspring with the same condition of parts. A man who had his little finger on the right hand almost cut off, and which in consequence grew crooked, had sons with the same finger on the same hand similarly crooked. The eminent physiologist Dr. Brown-Séquard mentions, that many young guinea-pigs inherited an epileptic tendency from parents which had been subjected to an operation at his hands resulting in the artificial production of fits; while a large number of guinea-pigs bred from animals which had not been operated on were not thus affected. At any rate, it cannot but be admitted that injuries and mutilations which cause disease, are occasionally inherited. But many cases of deformities existing at birth, as hare-lip, are not due to inheritance, although present in the father. They arise from a change effected in the child while in the womb, through an impression made upon the mind of the mother, as will be shown hereafter.
LATE MANIFESTATIONS OF THE EFFECTS OF INHERITANCE.
Not only are diseases inherited which make their appearance at birth, but those which defer their exhibition until a certain period of life corresponding with that at which they showed themselves in the parents. Thus in the Lambert family, before referred to, the porcupine excrescence on the skin began to grow in the father and sons at the same age, namely, about nine weeks after birth. In an extraordinary hairy family, which has been described, children were produced during three generations with hairy ears: in the father, the hair began to grow over his body at six years old; in his daughter somewhat earlier, namely, at one year; and in both generations the milk teeth appeared late in life, the permanent teeth being deficient. Greyness of hair at an unusually early age has been transmitted in some families. So, also, has the premature appearance of baldness.
HOW TO AVOID THE TENDENCY OF INHERITANCE.
These facts suggest the practical consideration, that in those diseases the predisposition to which alone is inherited, and which break out only after a lapse of time, it is often altogether possible to prevent the predisposition being developed into positive disease. Thus, for instance, the inherited tendency to consumption remains asleep in the system until about the age of puberty, or later. Therefore, by the use of a diet in which animal food forms a large portion, properly regulated, and systematic exercise in the open air, the practice of the long inhalations before recommended, warm, comfortable clothing, together with a residence, if practicable, during the changeable and inclement seasons of the year, in an equable climate, we can often entirely arrest the development of the disease. Prevention here is not only better than cure, but often all that is possible. Those in whom the disease has become active, must too often, like those who entered Dante's infernal regions, 'abandon hope.' Let our words of caution therefore be heeded.
When there is reason to believe that an individual possesses an inherent tendency to any disease, it is the duty of the medical adviser to study the constitution of the patient thoroughly, and after such study to recommend those measures of prevention best suited to avert the threatened disorder. Above all, let the physician look closely to the child at the period of life when any grave constitutional inheritable disease attacked the parent. This supervision should be carried into adult years, for there are instances on record of inherited diseases coming on at an advanced age, as in that of a grandfather, father, and son, who all became insane and committed suicide near their fiftieth year. Gout, apoplexy, insanity, chronic disease of the heart, epilepsy, consumption, asthma, and other diseases, are all more or less under the control of preventive measures. Some hereditary diseases, such as idiocy and cancer, we are impotent to prevent, in the present state of our knowledge.
A singular fact in connection with the transmission of disease is the readiness with which a whole generation is passed over, the affection appearing in the next. A father or mother with consumption may in some instances have healthy children, but the grandchildren will die of the disease. Nature kindly favors one generation, but only at the expense of the next.