There is reason to believe that the organisms may lie in a dormant condition for an indefinite period in these glands, and only become active long afterwards, when some depression of the patient’s health produces conditions which favour their growth.  When the organisms become active in this way, the tuberculous tissue undergoes softening and disintegration, and the infective material, by bursting into an adjacent vein, may enter the blood-stream, in which it is carried to distant parts of the body.  In this way a general tuberculosis may be set up, or localised foci of tuberculosis may develop in the tissues in which the organisms lodge.  Many tuberculous patients are to be regarded as possessing in their bronchial glands, or elsewhere, an internal store of bacilli, to which the disease for which advice is sought owes its origin, and from which similar outbreaks of tuberculosis may originate in the future.

The alimentary mucous membrane, especially that of the lower ileum and caecum, is exposed to infection by swallowed sputum and by food materials, such as milk, containing tubercle bacilli.  The organisms may lodge in the mucous membrane and cause tuberculous ulceration, or they may be carried through the wall of the bowel into the lacteals, along which they pass to the mesenteric glands where they become arrested and give rise to tuberculous disease.

#Relationship of Tuberculosis to Trauma.#—­Any tissue whose vitality has been lowered by injury or disease furnishes a favourable nidus for the lodgment and growth of tubercle bacilli.  The injury or disease, however, is to be looked upon as determining the localisation of the tuberculous lesion rather than as an essential factor in its causation.  In a person, for example, in whose blood tubercle bacilli are circulating and reaching every tissue and organ of the body, the occurrence of tuberculous disease in a particular part may be determined by the depression of the tissues resulting from an injury of that part.  There can be no doubt that excessive movement and jarring of a limb aggravates tuberculous disease of a joint; also that an injury may light up a focus that has been long quiescent, but we do not agree with those—­Da Costa, for example—­who maintain that injury may be a determining cause of tuberculosis.  The question is not one of mere academic interest, but one that may raise important issues in the law courts.

#Human and Bovine Tuberculosis.#—­The frequency of the bovine bacillus in the abdominal and in the glandular and osseous tuberculous lesions of children would appear to justify the conclusion that the disease is transmissible from the ox to the human subject, and that the milk of tuberculous cows is probably a common vehicle of transmission.

#Changes in the Tissues following upon the successful Lodgment of Tubercle Bacilli.#—­The action of the bacilli on the tissues results in the formation of granulation tissue comprising characteristic tissue elements and with a marked tendency to undergo caseation.