Tuberculosis of the lung, illustration. Tuberculosis infection of the lung in which the upper lobe presents with a firm, dense consistency, and the tissue is largely devoid of airways. The yellowish-colour cut surface is friable and crumbly representing confluent necrotic cellular debris. Infected lymphoid tissue is noted at the root of the lung. Small foci of infection occur in the lower lobe. Tuberculosis bacteria are resistant to the tissue macrophages that attempt to destroy them and will replicate inside macrophages eventually killing these cells resulting in granulomas and necrosis. From Bollinger, O. 1901 Atlas und Gundriss der Pathologischen Anatomie, vol 1. Lehmann, Munich.