_Vital Phenomena in Brute Bodies._—There is no doubt that certain phenomena of vitality may occur outside of the cellular atmosphere. And carrying this further, we may admit that they may be produced in certain slightly organized bodies (crushed cells), and then in certain unorganized bodies in certain brute beings. In every case it is certain that effects are produced at any rate similar to those which are characteristic of living matter. It is for observation and experiment to decide as to the degree of similarity, and their verdict is that the similarity is complete. The crystals and the crystalline germs studied by Ostwald and Tammann are the seat of phenomena which are quite comparable to those of vitality. CHAPTER IV. EVOLUTION AND MUTABILITY OF LIVING MATTER AND BRUTE MATTER. Supposed immobility of brute bodies—Mobility and mutability of the sidereal world.—§ 1. The movement of particles and molecules in brute bodies—The internal movements of brute bodies—Kinetic conception of molecular motion—Reality of the motion of particles—Comparison of the activity of particles with vital activity.—§ 2. Brownian movement—Its existence—Its character—Its independence of the nature of the bodies and of the nature of the environment—Its indefinite duration—Its independence of external conditions—The Brownian movement must be the first stage of molecular motion.—§ 3. Motion of particles—Migration of material particles—Migration under the action of weight; of diffusion; of electrolysis; of mechanical pressure.—§ 4. Internal activity of alloys—Their structure—Changes produced by deforming agencies—Slow return to equilibrium—Residual effect—Effect of annealing; effect of stretching—Nickel steel—Colour photography—Conclusion—Relations of the environment to the living or brute matter. One of the most remarkable characteristics of a living being is its evolution. It undergoes a continuous change. It starts from something very small; it assumes a configuration and grows; in most cases it declines and disappears, having followed a course which may be predicted—a sort of ideal trajectory. _Supposed Immobility of Brute Bodies._—It may be asked whether this evolution, this directed mobility, is so exclusively a feature of the living being as it appears, and if many brute bodies do not present something analogous to it. We may answer in no uncertain tones. Bichat was wrong when he contrasted in this respect brute bodies with living bodies. Vital properties, he said, are temporary; it is their nature to be exhausted; in time they are used up in the same body. Physical properties, on the contrary, are eternal. Brute bodies have neither a beginning nor an inevitable end, neither age, nor evolution; they remain as immutable as death, of which they are the image.