American practice of surgery : a complete system of the science and art of surgery . n of the cells, vacuolation, clear spaces between the cells, and a stringydetritus. Caseation.—Caseation is a term applied more or less loosely to designate that 216 a:\ierican practice of surgery. form of death of tissue which is characterized by the production of materialsomewhat resembhng cheese. It is to be regarded probably as a post-ne-crotic change rather than as a form of necrosis. Simple and coagulation necrosisand moist gangrene may be followed by caseation. Caseation is found typ-ically in certain o
American practice of surgery : a complete system of the science and art of surgery . n of the cells, vacuolation, clear spaces between the cells, and a stringydetritus. Caseation.—Caseation is a term applied more or less loosely to designate that 216 a:\ierican practice of surgery. form of death of tissue which is characterized by the production of materialsomewhat resembhng cheese. It is to be regarded probably as a post-ne-crotic change rather than as a form of necrosis. Simple and coagulation necrosisand moist gangrene may be followed by caseation. Caseation is found typ-ically in certain of the infectious granulomata, notably tuberculosis. Somewhatsimilar changes occur in gummata and in actinomycosis, and occasionally intumors. Caseous foci are opaque, grayish-white or yellow, more or less firmand granular, and are cheesy in consistence. If they are hard and dry, wespeak of the process as firm or hard caseation; if the imbibition of fluid hasoccurred, we speak of it as soft caseation. Microscopically, we find more or less extensive areas in which the normal out-. FiG. 70.—Caseation (Tuberculous) in the Lung. (Lcitz ohj. Xo. 3 ) Area of to theright; the blood-vessels injected to show the avascularity of the necrotic part. {From the authorsprivate collection.) lines of the cells and tissues are lost, the cells in various stages of disintegration,with liberation of their nuclear chromatin. In the larger areas the central por-tion is converted into a structureless, granular mass, consisting of cellular de-bris, fat, and sometimes calcareous salts. In some cases fibrin is present. In thecase of tuberculous caseation, it is believed that the necrotic change is due in partto obstruction of the nutrient blood-vessels, and in part to the influence of thetoxins produced by the bacilli (see Fig. 70). Somewhat similar caseation is occa-sionally observed in certain non-tuberculous inflammatory exudates in the lungs. Caseous foci may be completely absorbed and
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