All that has been written by different authors, by Cullen in particular, upon the nervous power, upon the action of the brain on the arterial system, is vague, illusory and contradicted by experiment. _Properties of Organic Life. Sensible Organic Contractility._ The sensible organic contractility is evidently wanting in the system of which we are treating. In whatever way we irritate an artery in a living animal, it remains uniformly immoveable. 1st. If we stimulate the external surface with a scalpel or any other instrument, it is easy to make this remark. 2d. The same observation is made when we excite the internal surface, an experiment that I have often made, because we know that the heart is more irritable internally than externally. 3d. An artery cut longitudinally in a living animal does not turn over at its edges like the intestines in similar circumstances. 4th. An arterial tube, drawn out of the body, never gives like the intestines, the heart, &c. any mark of contractility. 5th. If we raise the arterial plates, layer by layer, in a living animal or one recently killed, we see nothing of that trembling, that palpitation that the fibres of the organic muscles exhibit under like circumstances; on the contrary, we observe in them a kind of inertia very analogous to that of tendinous, aponeurotic fibres, &c. 6th. It is said, that by placing the finger in an artery, a contraction is felt. I have often made this experiment; the contraction is infinitely less sensible than has been said; besides it is produced evidently by the contractility of texture. 7th. Lamure says, that a portion of blood being intercepted between two ligatures in an artery, the parietes of it continue to contract, though deprived of the influence of the heart; this is not correct. It is so important that I have examined it myself; I have repeated this experiment at least ten times upon the carotid; the following has always been the result; the tube comprised between the two ligatures and filled with blood, is agitated by a real motion, but it is only that of the common locomotion that it partakes with the whole artery, and which arises from the impetus of the blood against the ligature nearest the heart. To be convinced of this, it is only necessary to lay bare a considerable portion of this artery; we see evidently that the whole tube, whether the portion nearest the heart, or that comprised between the ligatures, or that which is beyond, is agitated by a common motion. 8th. Instead of the blood I have intercepted different irritating fluids in a portion of an artery; there is the same inertia, the same want of contraction in the parietes; but the same motion derived from the general locomotion. 9th. Many authors have produced a contraction on the part of the arteries by stimulating them with concentrated acids. This is true, and I have also produced this effect; but it is not the result of contractility, but it is the horny hardening.