This primary exaltation of nervous force is produced by some to a very considerable extent, but by others very slightly. Of the three orders into which I have divided Narcotics, which are named from their respective actions upon the brain, Inebriants cause most, and Deliriants least, of this primary stimulation. In the second place, Narcotics depress nervous influence. This depression is not in a direct, but in an inverse ratio to the primary stimulation. The less the one, the greater the other. Thus the depression cannot be considered as the mere re-action from the stimulation, as supposed by Dr. Brown, for then there would be a direct relation between the two effects. But we find that the exhilarating action of Alcohol may often be followed by no manifest depression; and that Belladonna, which scarcely stimulates at all, exerts a very sensible depressing influence.
Regarded simply in their action on nervous force generally, the medicines of the first order of Narcotics would approach very nearly to Stimulants, and those of the third order to Sedatives. But Narcotics have all a power which is possessed by neither of the other divisions.
They influence the intellectual functions, _i.e._ the mind, and the physical ties by which mind is connected with matter. These physical ties are,--the functions of volition and sensation, by which the mind is connected with the body, moving it or feeling it; and the five senses, by which the mind, through the body, is connected with external things. These intellectual properties, the centre of which is the brain, are more or less affected by Narcotic medicines. The first action of the latter is, to exalt these functions, just as they first exalt nervous force in general. The degree of this exaltation varies, as in the former case. Inebriants stimulate the mind to a considerable degree; Soporifics less; and Deliriants possess least of this primary exciting power. But it is in their secondary action on the mind that we find the most characteristic difference between them.
On referring to the arrangement, it will be seen that I have divided Narcotics into the three orders to which I have already referred by name, and which are thus designated in Latin: