According to Laennec, one may speak of degeneration in two precise cases: when one tissue changes into another that exists in a different form and localization in the organism (osseous degeneration of the cartilages, fatty degeneration of the liver); and when a tissue assumes a texture or configuration that has no pre existing model (tuberculous degeneration of the lymphatic glands or of the pulmonary parenchyma; scirrhous degeneration of the ovaries or testicles).