Has been much confounded with medullary sarcoma, but the two diseases are materially different. Fungus hæmatodes almost always supervenes on other morbid formations, when they have been ulcerated and exposed; and the particular formation which most frequently precedes is the medullo-sarcomatous; a bleeding fungus, however, occasionally protrudes from tumours of a different character, which, though they may have been at first simple, have degenerated, ulcerated, and assumed a malignant action. The disease certainly does not occur so frequently as some have asserted; for many, instead of limiting the application of the term to those fungous protrusions which bleed, honour with the appellation of fungus hæmatodes every growth which protrudes after the ulceration of a tumour, and every tumour which is unusually prominent, of soft consistence, and of a somewhat fungous appearance, although such have never shown any disposition to bleed, either spontaneously, or from irritation. But fungus hæmatodes, as the name implies, is truly a fungus which resembles blood; and as bloody or blood-like tumours are formed from the rupture of some vessel of rather a large size, and as they almost invariably evince a tendency to profuse hemorrhage, as a necessary consequence of the mode of their formation, the term is correctly applied only to those fungous growths which either have at one time emitted a discharge of blood, and exhibit symptoms of a recurrence of the hemorrhage, or which frequently pour out a quantity of blood, sometimes inconsiderable, but often profuse, and generally altogether uncontrollable. In short, the circumstances necessary to entitle a morbid formation to the appellation of fungus hæmatodes are a fungous structure and appearance, and hemorrhage proceeding from it to a greater or less degree, and with more or less frequency. Fungi are frequently met with, but there are certainly few hæmatoid fungi.