It has also been urged against the theory of predisposition that members of tuberculous families are more exposed to infection, and that they are therefore more frequently afflicted with tuberculosis. Moreover the offspring of such families without a doubt show a dimin ished resistance to all harmful influences; the children of sickly and weakened parents are below the average in development and vital power. Epstein has pointed out the low average weight of infants of tuberculous mothers. I believe that we can speak of paratuberculaus manifestations in such children, following the analogy of the offspring of luctic parents. The offspring of tuberculous parents, without really having tuberculosis, at times show certain outward signs of malnu trition. To what extent we are dealing with specific tuberculous man ifestations in such children we cannot at present say. Other chronic and wasting diseases, especially when combined with poverty, may produce similar symptoms in the offspring. On the other hand, we find many children whose development is excellent in spite of a tuber culous taint.
We now come to the consideration of tuberculosis acquired during life and first of all to the so-called aerogenic infection. Until lately the opinion that the tubercle bacillus attacks the child through the respiratory tract was not only the accepted, but almost the uncon troverted view. In pediatric literature the cause of tuberculosis is always given as due to inhalation of the bacillus. Even for the infant this was supposed to hold good.
As a proof of this belief it was stated that in children the lungs and bronchial glands are the sites of most frequent invasion. This argument formerly seemed to me sufficient, and I too was of this opinion. Nor can it be gainsaid that tuberculosis may be acquired through the respiratory tract. For instance, if a mason should inhale an infected splinter of stone, he might develop an inhalation tuberculosis. Even in this case, however, we should rather expect a primary tuberculosis of the larynx or of the larger bronchi.
In childhood opportunity for inhalation of tubercle bacilli is espe cially afforded when the children live among tuberculous people. This condition is particularly dangerous when the child is able to crawl about on the floor.
But from the clinical standpoint the question at once presents itself why we so rarely find primary tuberculosis of the larynx or of the larger bronchi, conditions almost unknown in younger children. How is it that the inhaled bacilli do not lodge in these organs instead of penetrating to the remotest parts of the lungs and to the bronchial lymph-nodes? Such scepticism may be answered by quoting the large number of experiments whereby tuberculosis of the lungs was produced by inhaling powdered tuberculous material. These experiments always
gave positive results. But the possibility that the bacilli entered the intestinal tract as well as the inspiratory tract must be considered, and therefore the possibility that the infection was enterogenic in nature. We must uphold von Behring in his statement that such proofs of inhalation tuberculosis must be carefully and critically reviewed..
In spite of the fact that the basis for the theory of aerogenic in fection was far from sound, this belief gained general credence. Beh ring's startling communication in 1903 served to make us reconsider, and again brought forward the question of the enterogenic origin of tuber-. culosis. Behring maintained that tuberculosis of the lungs attacks the babe in its cradle, but that the milk which the infant drinks is the chief source of danger.
Behring's views must not be interpreted to mean that infection. is due solely to bovine bacilli, as he said even in his address at Cassel that the danger lay in milk which contains tubercle bacilli, irrespective as to whether the bacilli are of human or bovine origin. In a later article he emphasized this point and enlarged upon it, adding that bacilli which are transmitted from mouth to mouth in the act of kiss ing, or are inhaled with the dust of infected rooms, are all swept into the intestinal tract by the milk.
When these new views of Behring's were made known, the natural assumption was that following an enterogenie infection we should have to look for the primary focus in the intestinal tract and in its. lymph-nodes. But in direct contradiction to this theory, all investigations report that primary intestinal or mesenteric lymph node tuberculosis is an exceptionally rare occurrence, notwithstanding which Heller found primary tuberculosis in this region in 30.7 per cent. of his cases (140 autopsies on patients who died of diphtheria but showed some tuberculous lesion).
Three possibilities have been considered as regards the mode of intestinal infection: (1) that there develops a primary tuberculosis. of the intestine which gives rise to involvement of the mesenteric lymph nodes; (2) that the intestine becomes the seat of a nontuberculous infection and thus allows the passage of tubercle bacilli and other microorganisms through its walls; (3) that healthy intestines allow the passage of tubercle bacilli, more especially during childhood. Some facts add weight to this view.