We have seen in speaking of the passions, that the muscles of locomotion are brought into action in two manners. 1st, by the will; 2dly, by sympathy. This last mode of action occurs, when from the affection of an inward organ the brain is affected also, and occasions a motion which, in such case, is involuntary. A passion, for instance, affects the liver, the liver the brain, the brain the voluntary muscles. Here it is the liver, not the brain, which is the principle of motion: so that the muscles, though always thrown into action, immediately from the irradiations of the brain, belong nevertheless, as to their functions, sometimes to the one life, sometimes to the other. Hence it is easy to conceive in what way the fœtus moves: with the fœtus, locomotion is not a portion of the animal life; its exercise does not suppose a pre-existent will; it is purely a sympathetic effect. In utero the phenomena of the organic life succeed each other with an extreme rapidity; a thousand different motions are incessantly connected in the organs of circulation and nutrition. In these, every thing is energetically in action. But this activity of the organic life supposes a frequent influence exerted upon the brain by the inward organs, and consequently as many reactions on the part of the brain by sympathy upon the muscles. Besides, the brain is at such time more susceptible of such sort of influence, being much more developed than the other organs, and entirely passive on the side of the sensations. We may now conceive what the motions or the fœtus are. They belong to the same class as many of those of the adult, which have not been as yet sufficiently distinguished. They are the same as those which are produced in the voluntary muscles by the passions; they resemble those of the man who sleeps, and who moves without dreaming, for nothing is more common than violent agitation in sleep succeeding difficult digestion. The stomach is in strong action; it acts upon the brain; the brain upon the muscles. I might find a number of other involuntary organic motions taking place in the voluntary muscles of the adult, and consequently adducible to my present purpose; but what I have said on this subject will suffice. Let us remark only, that the organic motions, as well as the sympathetic affection of the brain, which is the seat of them, must gradually dispose this organ, and the muscles of the fœtus, the one to the perception of sensations, and the other to the motions of the animal life, which are to commence after birth. But on this head I shall refer to the memoirs of Monsieur Cabanis.