The question of acidosis in tuberculosis is still a debatable one. Pottenger1 states that "there are probably many factors present in tuberculosis which have a tendency to increase acidosis, such as deficient intake of oxygen, deficient excretion of carbon dioxid, which occurs particularly in the disease, as a result of diminished pulmonary area, etc. Klebs2 takes the opposite view, that "the gaseous metabolism in tuberculosis is but slightly, if at all, altered, the system accommodating itself to the lessened lung area, and, as is usual in the body, accomplishing the same amount of work with the decreased amount of tissue." A. Loewy, and Kraus and Chvostek3 found a moderate increase in oxygen intake and carbon dioxid excretion in cases of pulmonary tuberculosis. It will be one of the objects of this work to show that in far advanced cases of pulmonary tuberculosis with considerable destruction of lung tissue by cavitation