Neurotics are thus applied to various symptoms, and to many disorders. Their different modes of action will be detailed more at length presently. It must be remembered that all these actions, powerful though they may be, are transitory. The effect produced on the nerve is not a lasting one, and no essential change in the blood is effected by true Neurotics. They are not natural elements of this fluid, but must quickly pass out of it; and they having thus left it, their action also is over. Thus the truth of the fifth minor proposition is plain. I will now attempt to give a brief but distinct account of the three divisions into which I have divided this class of medicines. STIMULANTS. Stimulants are medicines which pass from the blood to the nerves or nerve-centres, and act on them so as to exalt nervous force, in general or in particular. That is, they may extend their operation more or less to the whole nervous system, having a general tendency to communicate nervous energy; or they may confine their action to particular departments of this system, having no manifest influence on other parts. On referring to the arrangement at the commencement of the Essay, it will be seen that Stimulants are subdivided, according to whether their action is thus extended or confined. STIMULANTIA. Ord. 1. Stimulantia generalia. Ord. 2. Stimulantia specifica. The first order includes all the medicines that are commonly understood to be Stimulants. But as the remedies of the second order obviously exalt nervous force, the term applied to the others on that ground could not consistently be withheld from them, although their action is more limited and local in its nature, being confined to a certain part of the body, and to certain nerves. The same remark may be made of the order of Special Sedatives, which will soon have to be considered. ORD. I. GENERAL STIMULANTS. (_Mineral substances._--Ammonia and its Carbonates. Phosphorus. _Animal substances._--Musk, and Castor. _Vegetables containing volatile oils._--The aromatic Labiatæ, Compositæ, and Umbelliferæ. Cloves and Nutmeg. Cinnamon, Cassia, Sassafras. Rue, Barosma. The Aurantiaceæ. Canella. Valerian. Mustard. Cajeput and Pimenta. Hops. Juniper, Turpentine. Cardamom. Onion. _Vegetables containing acrid principles._--Senega. Horseradish. Serpentary. Cascarilla. Pepper. Contrajerva. Ginger. Capsicum. Mezereon. _Resinous substances._--Guaiacum. Mastich, Olibanum, Myrrh, Elemi. Copaiba. Peru, Tolu. Assaf[oe]tida, Ammoniacum, Galbanum. Benzoin, Storax. Pine resin.)