But no animal possesses this extreme solidarity of the parts of the living economy. It is a philosopher’s dream. It is the dream of Kant, to whom the perfect organism would be “a teleological system,” a system of reciprocal ends and means, a sum total of parts each existing for and by the rest, for and by the whole. An organism so completely connected would be unlikely to live. In fact, living organisms show a little more freedom in the interplay of their parts. Their nervous apparatus fortunately does not attain this imaginary perfection; their unity is not so rigorous. The idea of individuality, of individual existence, is therefore not absolute but relative. There are all degrees of it according to the development of the nervous system. What the man in the street and the doctor himself understand by death is the situation created by the stopping of the general wheels, the brain, the heart, and the lungs. If the breath leaves no trace on the glass held to the mouth, if the beating of the heart is no longer perceptible by the hand which touches or the ear which listens, if the movement and the reaction of sensitiveness have ceased to be manifest, these signs make us conclude that it is death. But this conclusion, as we have said before, is a prognostic rather than a judgment of fact. It expresses the belief that the subject will certainly die, and not that it is from this moment dead. To the physiologist the subject is only on the way to die. The process has started. The only real death is when the universal death of all the elements has been consummated. 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.