_In the lymphatic structures and lymph nodes_ tuberculosis is a most frequent affection. In these localities it may occasionally be primary, but is almost always a secondary lesion. It is in separating from the lymph stream the tubercle bacilli, which would otherwise be passed into the general circulation, that the lymph nodes, acting as filters, render us the greatest possible service. These filters themselves, however, almost always become infected, and, enlarging, they assume the appearances known to the laity as _scrofula_, which have been generally referred to as _scrofulous glands_. These lesions abound rather about the axilla and the cervical and bronchial nodes than about the lower extremities. Nevertheless, the retroperitoneal, mesenteric, and inguinal nodes are occasionally infected. In these nodes will be found giant cells surrounded with epithelioid cells, containing bacilli and undergoing cheesy degeneration or suppuration. Infection often proceeds from centre to periphery, and then to the surrounding tissues, the filter, as such, having become so choked that nothing seems to pass it. By virtue of this surrounding infiltration (which used to be known as _peri-adenitis_, when lymph nodes were spoken of as _lymph glands_) generalized infection is in some measure prevented, while the natural barriers are altered and natural distinctions between tissues are lost. This makes complete extirpation of these tuberculous foci often very difficult, while the adhesions which they contract, for instance in the neck, are often to the large vessels and nerve sheaths, by all of which their operative treatment is naturally complicated. When infection from the superficial nodes extends toward the surface it is easily recognized by the dusky hue of the overlying skin, the hardness, infiltration, and, later, the fixation, of these masses, accompanied usually by evidences of suppuration. _In and on the serous membranes_ we find tuberculous lesions, either primary or metastatic, usually miliary in type. In the _pleural cavity_ they produce effusion (hydrothorax), which may necessitate repeated paracentesis, or by a mixed or secondary infection may cause empyema, for which much more radical and even extensive operations are demanded. (See Thoracoplasty.) In the case of the _peritoneum_ we find (_a_) miliary tuberculosis, (_b_) a slower non-exudative form with firm, sometimes pigmented nodules, and (_c_) a form characterized by small gummas which become caseous, coalesce, and ulcerate, binding together intestinal coils and producing extensive and irregular adhesions, with seropurulent exudation, often enclosed in walled-off sacs. In all of these cases surgical intervention should be considered, while in the more acute miliary forms abdominal section, with flushing, has in many instances afforded relief.