_Phenomena Common to Living Beings._—Nature shows us an infinite number of beings, animal or vegetable, described in ordinary language as _living beings_. This language implicitly assumes something common to them all, a universal manner of being which belongs to them without distinction, without regard to differences of species, types, or kingdoms. On the other hand, anatomical analysis teaches us that animated beings and plants may be divided into parts ever decreasing in complexity, of which the last and the simplest is the _anatomical element_, the _cell_, the microscopic organic unit which, too, is alive. Common opinion suspects that all these beings, whether entire as in the case of animal and vegetable individuals, or fragmentary as in the case of cellular elements, have the same manner of being, and present the same body of common characteristics which rightly gives them this unmistakable title of living beings. Life then essentially would be this manner of being, common to animals, vegetables, and their elements. To seize in isolation these common, necessary, and permanent features, and then to synthetize them into a whole, will be the really scientific method of defining life, and of explaining its nature. And here then immediately arises a fundamental question which gives one pause, a question of fact which must be solved before we can go further. Is there really a common manner of being in all these things? Are _animal life, vegetable life_, and the life of the elements or _elementary life_, all the same? Is there a sum total of characteristics which may define life in general? The physiologists, following in the steps of Claude Bernard, respond in the affirmative. They accept as valid and convincing the proof given of this vital community by the illustrious experimentalist. However there are some rare exceptions to this universal assent. In this concert of approval there is at least one discordant voice, that of M. F. Le Dantec.[13] [13] M. Le Dantec, of whose philosophical and rigorously systematic mind I have the highest opinion, has laid down a new conception of life, the essential basis of which is this very distinction between elementary life and ordinary life; between the life of the elements or of the beings formed from a single cell, protophytes and protozoa, and the life of ordinary animals and plants, which are multicellular complexes, and for that reason called _metazoa_ and _metaphytes_.