and may even attack whole cells. But to me it seems probable that their rôle is entirely secondary. They do not cause the death of cells, but they feed presumably only upon cells which are already dead or at least dying. Their activity is to be regarded, so far as the problem of the death of cells is concerned, not as indicating the cause of death, but as a phenomenon for the display of which the death of the cell offers an opportunity. The subject of the death and disintegration of cells is an exceedingly complex one, and might well occupy our attention for a long time. But it is not permissible to depart from the strict theme which we have before us, and I will content myself, therefore, with throwing upon the screen two tables[1] which illustrate to us the variations in the death of cells and in their modes of removal which are
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I. Death of Cells First. Causes of death. A. External to the organism: (1) Physical (mechanical, chemical, thermal, etc.). (2) Parasites. B. Changes in intercellular substances (probably primarily due to cells): (1) Hypertrophy. (2) Induration. (3) Calcification. (4) Amyloid degeneration (infiltration). C. Changes inherent in cells: Second. Morphological changes of dying cells. A. Direct death of cells: (1) Atrophy. (2) Disintegration and resorption. B. Indirect death of cells: (1) Necrobiosis (structural change precedes final death). (2) Hypertrophic regeneration (growth and structural change often with nuclear proliferation precede final death). Third. Removal of cells. A. By mechanical means (sloughing or shedding) B. By chemical means (solution). C. By phagocytes. II. Indirect Death of Cells A. Necrobiosis. (1) Cytoplasmic changes: (a) Granulation. (b) Hyaline transformation. (c) Imbibition. (d) Desiccation. (e) Blasmatosis. (2) Nuclear changes: (a) Karyorhexis. (b) Karyolysis. B. Hypertrophic degeneration. (1) Cytoplasmic: (a) Granular. (b) Cornifying. (c) Hyaline. (2) Paraplasniic: (a) Fatty. (b) Pigmentary. (c) Mucoid. (d) Colloid, etc. (3) Nuclear (increase of chromatin).
