[37] We know that the organs are nourished, that the glands secrete, we know that certain vessels absorb (whether they be the lymphatics or not,) but we do not know, that all this is produced by a _partial oscillatory movement in each fibre, in each molecule_. No one can be certain that this movement takes place, because no one has seen it. [38] Why invent a new word, when we have that of elasticity, which expresses for all bodies whether organic or inorganic, that tendency to resume their usual form and size, when the cause that made them change them is no longer in exercise? [39] Bichat here unites three sorts of motion which have no relation between them; the systole of the cavities of the heart should be considered as a really active dilatation. The increase of size of the corpora cavernosa, which is an effect purely passive of the accumulation of blood in those parts, and which can be produced after death by artificially accelerating the circulation in them; and finally, the motion of the iris, a motion evidently produced by a muscular contraction, excitable by galvanism or pricking the nerve. [40] Without denying the influence which the capillary systems of the different organs have on the circulation, we have shown that even in the veins the action of the heart is felt and modifies the course of the blood. CHAPTER VIII. OF THE ORIGIN AND DEVELOPMENT OF THE ANIMAL LIFE. If there be any circumstance, which establishes a real line of demarcation between the two lives, this circumstance undoubtedly is the mode and epoch of their origin. The organic life is active from the very first moment of our existence; the animal life begins after birth only; for without external excitants the latter is as necessarily condemned to inaction, as without the fluids of the œconomy, which are its internal excitants, the former would become extinct. But the subject, on which we are now engaged deserves a more particular discussion, and in the first place let us examine, in what manner the animal life, which for some time is absolutely null, is born as it were and developed. I. _In the fœtus the first order of the functions of the animal life is not as yet in action._ The instant, at which the fœtus begins to exist, is nearly that of its conception; but this existence, the sphere of which is every day enlarged, is not the same as that, which the child is destined to enjoy after birth. The state, in which the fœtus exists while in the womb, has been compared to that of a profound sleep. Such comparison is inexact. In a state of sleep the animal life is only in part suspended. In the fœtus it has not commenced. We have seen in fact, that this life is made up of the simultaneous or distinct exercise of the senses, of the nerves, of the brain, of the organs of locomotion, and the voice. Now in these different functions every thing in such state is inactive.