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 CHAPTER III.

PHYSICAL AND CHEMICAL CHARACTERS OF CELLULAR DEATH. NECROBIOSIS. GROWING OLD.

Characteristic of elementary life—Changes produced by death in the composition and the death of the cell—Schlemm; Loew; Bokorny; Pflüger; A. Gautier; Duclaux—The processive character of death—Accidental death—Necrobiosis—Atrophy—Degeneration—So-called natural death—Senescence—Metchnikoff's theory of senescence—Objections.

Elementary death is nothing but the suppression in the anatomical elements of all the phenomena of vitality.

Characteristics of Elementary Life.—The characteristic features of elementary life have been sufficiently fixed by science. First of all, there is morphological unity. All the living elements have an identical morphological composition. That is to say that life is only accomplished and sustained in all its fulness in organic units possessing the anatomical constitution of the cell, with its cytoplasm and its nucleus, constituted on the classical type. In the second place, there is chemical unity. The constituent matter, the matter of which the cell is built up, diverges but little from a chemical type—a proteid complex, with a hexonic nucleus, and from a physical model which is an emulsion of granulous, immiscible liquids, of different viscosities. The third character consists in