THE HEREDITY OF TUBERCULOSIS Direct heredity of tuberculosis may be explained in two ways: Either the disease may be present in its true form at birth or in the foetus (congenital tuberculosis), or the bacilli may be carried from the parents to the offspring and remain temporarily latent, only to show their blighting influence when an opportunity presents itself (hereditary tuberculosis). In either case there is a real transmission of the bacilli in one form or another, and not merely the inheritance of a predispo sition, a certain increased susceptibility to tuberculosis, which sooner or later may lead to disease. We shall later return to the question of predisposition.
The possibility of infection of the foetus with tuberculosis is quite certain. There are a number of cases both in human beings and in animals which are unquestionable and therefore establish the fact without doubt.
The number of such cases considered reliable and unimpeachable varies according to the degree of scepticism with which one approaches the subject.
About twenty cases in man and some hundreds in cattle are sub stantiated in every particular. Huss accepts 40 human and about 100 bovine cases. Thieme examined the foetuses of 86 tuberculous cows and found 2 tubercular. In one case the placenta was also examined and showed tuberculous changes. Klepp found among 4068 newborn calves 0.64 per cent. suffering from congenital tuberculosis, and in another series, among 847 calves, 1.18 per cent. Trustworthy reports of congenital tuberculosis in calves are frequently recorded; among such are those of Johne in 1SS5, Nocard in 1896, etc.
As a type of a convincing case in human pathology I shall cite that of Lehmann: Woman, 40 years of age, in the ninth month of pregnancy, having suffered from tuberculosis for a long period, died three days after de livery. Autopsy showed old pulmonary tuberculosis, miliary tubercles throughout both lungs, scattered omental tubercles, tuberculous men ingitis. Peritoneum and uterus, including placental surface, free from macroscopic tuberculosis. The child died 24 hours after birth. Au topsy showed aortic lymph-nodes the size of a pea or bean, yellow, cut surface, granular. The bronchial lymph-nodes were still larger and
appeared- as a mass the size of a cherry, with cut surface as above. The lungs contained submiliary nodules, some as large as the head of a pin. Liver, spleen, and kidneys showed miliary tuberculosis. The nodules of all these organs proved to be tubercles of varying age, con taining numerous bacilli. The age of the tubercles, according to the microscopic picture must he judged to have been over a week; the lymph-node tuberculosis of far longer standing.
However, although we must recognize the possibility of heredi tary tuberculosis in man, it must be looked upon as very rare. Berend inoculated with tuberculin four children of tuberculous mothers and many born of healthy mothers, but did not obtain a positive reac tion in a single case. I myself attempted to diagnose tuberculosis in early infancy by means of tuberculin, but in more than 200 cases did not meet with a case of congenital tuberculosis, in spite of the fact that I gave especial attention to children of tuberculous mothers, in whom the clinical diagnosis had been substantiated by means of the tuberculin test.
The question of hereditary tuberculosis is far more difficult to settle. Not that there can be any doubt that it does exist, but because it is not easy to estimate the importance of heredity in the etiology of the disease. Hereditary tuberculosis, i.e., the passage of living and Hilt lent tubercle bacilli from the mother to the offspring certainly occurs.
The first proof of the passage of tubercle bacilli from the maternal blood into the fatal placenta and into the fatal liver was offered by Birch-Hirschfeld and Schmorl. They performed a Ca‘sarean section post mortem upon a woman who died of miliary tuberculosis and re moved the child who had died just previous to its mother. Since then, many cases have been reported, among which are some certainly open to question, as to whether hereditary or congenital tuberculosis existed. In such cases, a few days or weeks after birth, an advanced tubercu losis was found.