From all these facts, we cannot, I think, call in question the influence of the spinal marrow upon motion, the principle of which it receives from the brain and afterwards transmits it to the nerves. These last carry this principle, which they have received, to the muscles, either by means of the spinal marrow, as in almost all those of the trunk and the extremities, or directly from the brain, as in those of the face, the tongue, the eyes, &c. There are the same proofs for this nervous influence, as for that of the preceding sensitive organs. The tying, division or compression of a nerve paralyzes the corresponding muscle. Irritate with any agent a nerve laid bare in an animal, convulsive contractions are immediately seen in the muscle. These experiments have been so often and so accurately repeated by many authors, that I think it useless to go into details, which the reader may find everywhere. Irritation continued some time upon one point of the nerve destroys its influence upon the muscle, which remains immoveable; but it is put in motion again, if the irritation is carried to a lower part of the nerve. If we tie it, the motion ceases, if irritation is made above the ligature, it returns when it is made below, or when the ligature is removed. I would remark that all the nerves of animal life do not appear to be equally capable of transmitting to the muscles the different irradiations of the brain. In fact whilst in diseases, in wounds of the head, in our experiments, &c. the muscles of the extremities are convulsed or paralyzed with great ease, those of the abdomen, the neck, and especially the chest do not exhibit these phenomena, except when the causes of excitement and debility are carried to the highest point. Nothing is more frequent than to see the abdomen and the chest with their ordinary degree of muscular contraction, whilst the extremities or the face are agitated with convulsive motions. Examine most hemiplegias; the mouth is twisted, the superior and inferior extremity of one side become immoveable, and yet the pectoral and abdominal motions continue. Those of the larynx are more easily interrupted than these in paralysis; hence the different injuries of the voice. We could make a scale of the susceptibility of the muscles to receive the cerebral influence, or of the nerves to propagate it, for it is difficult to determine to which of these two causes the phenomenon is owing; we could, I say, make a scale, at the top of which should be placed the muscles of the extremities, then those of the face, then those of the larynx, afterwards those of the pelvis and the abdomen, and finally the intercostals and diaphragm. These last become convulsed and paralyzed with the most difficulty of all. Observe how this scale is adapted to that of the functions. What would become of life, which is always actually connected with the soundness of respiration, if all the cerebral lesions were as easily felt by the diaphragm and the