Figure 1. Characteristic pathologies of human post-primary TB from the 19^th and 21^st centuries.

Each pair of figures shows a drawing from the 19^th century paired with a 21^st century photomicrograph. The caseating granuloma is the characteristic lesion of primary TB. Post-primary TB begins a paucibacillary lobular pneumonia (Acute) that may undergo caseous necrosis (Acute Caseating), regress (Subacute Dry) or fibrose (Chronic Fibrosing). Finally, caseating granulomas in post-primary TB form only in response to caseous necrosis and are never the cause of it ²² (Post-primary Granuloma). The first 5 drawings are by Cornil and Ranvier (1881) ¹⁴, The last one is by Hamilton (1883) ¹⁵. The sections are H&E or trichrome stained and photographed at 40 to 400×.