snail that has had its head cut off remains alive, and after some weeks a new head grows on, together with horns; with this consciousness and ideas again appear; while till then the snail had only given evidence of blind will through unregulated movements. Thus here also we find the will as the substance which is permanent, the intellect, on the contrary, conditioned by its organ, as the changing accident. It may be defined as the regulator of the will.
It was perhaps Tiedemann who first compared the cerebral nervous system to a parasite (Tiedemann und Trevirann's Journal für Physiologie, Bd. i. § 62). The comparison is happy; for the brain, together with the spinal cord and nerves which depend upon it, is, as it were, implanted in the organism, and is nourished by it without on its part directly contributing anything to the support of the economy of the organism; therefore there can be life without a brain, as in the case of brainless abortions, and also in the case of tortoises, which live for three weeks after their heads have been cut off; only the medulla oblongata, as the organ of respiration, must be spared. Indeed a hen whose whole brain Flourens had cut away lived for ten months and grew. Even in the case of men the destruction of the brain does not produce death directly, but only through the medium of the lungs, and then of the heart (Bichat, Sur la Vie et la Mort, Part ii., art. ii. § 1). On the other hand, the brain controls the relations to the external world; this alone is its office, and hereby it discharges its debt to the organism which nourishes it, since its existence is conditioned by the external relations. Accordingly the brain alone of all the parts requires sleep, because its activity is completely distinct from its support; the former only consumes both strength and substance, the latter is performed by the rest of the organism as the nurse of the brain: thus because its activity contributes nothing to its continued existence it becomes exhausted, and only when it pauses in sleep does its nourishment go on unhindered.
