LOCATION OF THE PRIMARY LESION OF PULMONARY TUBERCULOSIS.

Birch--Hirschfield¹ made a careful examination of thirty-four cases of latent beginning pulmonary tuberculosis with the special purpose in view of determining the exact place in the lung where the tuberculosis first begins. The bodies examined were those of apparently previously healthy individuals, who had died suddenly. He reaches the conclusion that the general belief that pulmonary tuberculosis in the adult begins as a caseous lobular pneumonia does not correspond with the facts. Interstitial tubercle formation is also exceptional as the primary form of lesion. In the majority of cases the first focus consists in a subepithelial tuberculosis infiltration in the mucous membrane of a bronchus of medium caliber of from the second to the fifth order, according to the usual designation. The peribronchial tissue is secondarily involved. On account of this infiltration the lumen of the bronchus becomes narrowed or closed completely, and the corresponding part of the lung