_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 the possession of a _specific form_ acquired, preserved, and repaired by the element. The fourth character, and perhaps the most essential of all, is _the property of growth_ or _nutrition_ with its consequence, namely, a relation of exchanges with the external medium, exchanges in which oxygen plays considerable part. Finally, there is a last property, that of _reproduction_, which in a certain measure is a necessary consequence of the preceding,—_i.e._, of growth. These five vital characters of the elements are most in evidence in cells living in isolation, in microscopical beings formed of a single cell, protophytes and protozoa. But we find them also in the associations formed by the cells among one another—_i.e._, in ordinary plants and animals, multicellular complexes, called for this reason metaphytes and metazoa. Free or associated, the anatomical elements behave in the same way—feed, grow, breathe, digest in the same manner. As a matter of fact, the grouping of the cells, the relations, proximity and contiguity, which they assume, introduce some variants into the expression of the common phenomena; but these slight differences cannot disguise the essential community of the vital processes. The majority of physiologists, following Claude Bernard, admit as valent and convincing the proof that the illustrious experimenter furnished of this unity of the vital processes. There are, however, a few voices crying in the wilderness. M. Le Dantec is one. In his new theory of life he amplifies and exalts the differences which exist between the elementary life of the proteids and the associated life of the metazoa. In them he can see nothing but contrasts and deviations. If this is elementary life, let us ask what is _elementary death_—_i.e._, the death of the cell. And in this connection let us ask the questions which we have to examine in the case of animals high in organization, and of man himself. What are the characteristics of elementary death? When the cell dies, is its death preceded by a growing old or senescence? What are the preliminary signs and the acknowledged symptoms?