The blood supply of the lung in pulmonary tuberculosis.

Opinion appears to differ regarding the pathology of the vessels in lungs affected by miliary and chronic tuberculosis. Kaufmann (1929) emphasized obliterative changes in the pulmonary arteries. Boyd (1950) speaks of an endarteritis obliterans in vessels without specifying their origin. Cahnette (1923) mentioned the formation of small pedunculated, pear-shaped " aneurysms of Rasmussen " in branches of the pulmonary artery which traverse the walls of tuberculous cavities. The same aneurysmal dilatations were also pointed out by Kaufmann. Pagel (Kayne, Pagel, and O'Shaughnessy, 1948), on the other hand, believes that younger tubercles, and even older foci, contain blood vessels. He contends that the cells participating in the formation of the tubercle are generally derived from elements of connective tissue " which have an inherent tendency to vessel formation." Thus young tuberculous tissue is rich in capillaries and older foci are vascularized at the periphery. Coryllos (1933) speculated on the possible clinical significance ofendarteritis in the pulmonary arteries, and thought that this was probably beneficial in controlling the activity of tubercle bacilli. He considered that collapse therapy accomplished the same purpose by reducing the pulmonary artery bed and resting the lung. The oxygen requirements of the tubercle bacillus would thus be interfered with and its activity curtailed. Cournand and Richards (1941) also attribute the benefits ofcollapse therapy to the reduction of oxygen and blood available to the tubercle bacilli in the affected lungs. Rich (1944) thinks it reasonable to presume that the exacting oxygen requirements of the tubercle bacillus play some part in limiting its multiplication in vivo, and particularly within tuberculous lesions. Although little is known of the rate at which oxygen diffuses into areas of