I have given this designation to a class of sedatives which act immediately upon the cerebral centres, or those of relation, as well as upon the organic nervous centres, including those which control the functions of respiration and circulation. in other words, they are medicines which directly depress the cerebral as well as the spinal functions, and indirectly those of the lungs and heart. They bear to the nervous sedatives a similar relation to that which the cerebral stimulants bear to the nervous stimulants. The nervous sedatives in their depressing, as the nervous stimulants in their excitant influence, often leave consciousness, intellect, and emotion comparatively little disturbed. The cerebral sedatives, like the cerebral stimulants, powerfully affect these functions, the former directly depressing, the latter directly exciting and indirectly depressing them. it may at first sight seem strange, that the phenomena produced by these two latter classes, which operate in exactly opposite directions, should to a certain extent be the same. Thus drowsiness, insensibility, and loss of consciousness result both from the cerebral stimulants and cerebral sedatives. But there is this difference, that they are the indi-rect effects of the former, and the direct effects of the latter. The cerebral stimulants primarily excite the cerebral functions, which subsequently become impaired through the overwhelming congestion of the nervous centres; the cerebral sedatives produce the latter effect immediately, without any preliminary excitation. Under the influence of the one class, the loss of consciousness proceeds from an active congestion of the centres so great as to suspend their function, just as active hepatic congestion suspends the secretion of bile; under that of the other, a similar loss of consciousness follows from a direct diminution of the power to act, just as the liver ceases to secrete when depressed into a state of torpor. But, while the cerebral sedatives thus operate specially upon the functions of the brain, they also, like the nervous sedatives, depress those of the medulla oblongata and spinal marrow, and reduce respiration and circulation; thus differing from the latter class simply by the superaddi-tion of a more decided cerebral influence. in treating of the cerebral stimulants, I observed that most of them might be employed, in small doses, insufficient materially to affect the brain, for the same purposes as the nervous stimulants. in like manner, the cerebral sedatives, in quantities inadequate to the production of their characteristic cerebral phenomena, may serve the same practical purposes as the nervous sedatives. The more powerful of this class of medicines are extremely dangerous if abused, from their tendency directly to prostrate all the great vital functions. The cerebral stimulants, when given so largely as to destroy life, do so through a previous exaltation of the stimulated centres; and consequently there is an intermediate stage, before the fatal depression can ensue. From the cerebral sedatives, largely given, the danger is immediate.* Therefore, though there may be in nature many substances having the powers which characterize the present class, few of them have been introduced into use. Their powerfully poisonous properties have tended to discourage experiment. Of the therapeutic applications of those in use, it will be sufficient to treat under the articles themselves, as they are severally considered.

Before treating of the several medicines of the class, I will call attention to certain influences, of a mental character, which may often be advantageously applied to similar practical purposes.