The Cleveland medical journal . 734 The Cleveland Medical Journal of pathologists and physiologists. Great care must be taken incalling a process one of metaplasia, for the distinctions betweenthe various processes of true growth are not as sharply definedas we oftimes are led to believe. Metaplasia of a tissue, accord-ing to Ziegler (20), is that process by which an already fullydeveloped tissue is changed into another tissue without passingthrough an intermediate cellular stage. The relation to the retro-grade changes is a very close one, for in the modification of formthe cellular prolifera
The Cleveland medical journal . 734 The Cleveland Medical Journal of pathologists and physiologists. Great care must be taken incalling a process one of metaplasia, for the distinctions betweenthe various processes of true growth are not as sharply definedas we oftimes are led to believe. Metaplasia of a tissue, accord-ing to Ziegler (20), is that process by which an already fullydeveloped tissue is changed into another tissue without passingthrough an intermediate cellular stage. The relation to the retro-grade changes is a very close one, for in the modification of formthe cellular proliferation is either very slight or altogether absent. Metaplasia is a common physiological process occurring inthe body at all the periods of life. The most common examplesare the conversion of connective tissue cells into fat cells andcartilage into bone. We must differentiate, however, several closely alliedprocesses; namely, heterotopia, in which we have a congenital oracquired abnormal snaring of cells of an organ or tissue with. Fig. 7. Various types of marrow cells. Giant cells at A and and eosin x 500. subsequent growth out of place, and heteroplasia, upon whichSchriddle (21) has so ably written, in which a tissue of foreignnature is found growing in an abnormal situation; and anaplasia,by which is understood the loss of differential characters by tissuesunder abnormal conditions. Metaplasia is always bound by rathernarrow limits. Nowhere do we find this process involving theevolution of a more highly specialized tissue from less highly de-veloped tissue. Probably the best examples of pathological metaplasia, and:surely the most frequently written about are those afforded by Ruh—Metaplastic Bone and Marrow Formation 735 the metaplastic formation of bone. Ribbert (22) holds thatphysiological metaplasia is of frequent occurrence, but that truepathological metaplasia is a much rarer phenomenon than isusually contended. He holds that most of the cited examplesof h
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmedicine, bookyear191
