Necrosis

[nek-ro’ ’-sis) \yzKpoq, corpse]. The death of cells surrounded by living ti ue. Necrosis proper refers to death in ma , necrobiosis to death of individual cells. Among the causes of necrosis are: direct injury, obstruction of the circulation, lo of trophic influence. The varieties of necrosis are: coagulative necrosis, liquefactive necrosis, cheesy necrosis, dry, and moist gangrene. Necrosed ti ues may be absorbed, retained, or thrown off. The dead ti ue is called sequestrum in case of bone, and sphacelus in case of soft parts. In surgery the term necrosis is often applied specifically to the death of bone. Necrosis of bone is divided into N., Superficial, when the portion of bone just beneath the periosteum is affected; N., Central, when the internal portions are involved, and N., Total, when the bone through its entire thickne is necrotic. N., Balser’s Fatty. See Diseases, Table of. N., Cheesy, necrosis characterized by the formation of a cheese-like material. It is usually due to the presence of the tubercle bacillus, and is most often seen in the lungs. N., Coagulation-, N., Coagulative, a variety characterized by the formation of fibrin. It is most common in the blood, in thrombosis. It also occurs on mucous membranes, where it produces a false membrane, chiefly under the influence of the bacillus of diphtheria, but also of other irritant agents. Occasionally it occurs in the interior of organs as the result of embolism or thrombosis, leading to the formation of an anemic infarct. N., Colliquative. See N., Liquefactive. N., Embolic, coagulative necrosis in an anemic infarct following embolism. N., Liquefactive, a proce analogous to coagulative necrosis, but instead of fibrin the peculiar reaction of fluids and cells gives rise to the formation of a liquid. N., Mercurial, a necrosis of bones due to chronic poisoning with mercury. N., Phosphorus-, a necrosis of bone, especially of the lower jaw, occurring in those exposed to the fumes of phosphorus. N. ustilaginea, dry gangrene from ergotism. 431