These arc diffusible stimulants operating especially on the circulatory-function, with little comparative influence on the nervous system. They have sometimes been called Incitants or Simple Stimulants; but it has seemed to me that the name here given best expresses their peculiar character. Of course, they in some degree affect the nervous system; for one great general function can scarcely be considerably excited without more or less involving the others; but their primary and prominent action is upon the heart and arteries.

The obvious effects produced by the arterial stimulants, as a class, are a sensation of warmth or heat in the stomach, increased frequency and force of pulse, and augmented temperature of the surface. They, in general, also act as powerful irritants to the skin when directly applied to it, and indeed to any sensitive part with which they may come into contact. Each one, however, has characteristic properties, distinct from that of simple diffusible stimulation.

They may be employed in all cases calling for stimulation, when the action of the heart is depressed, and are frequently thus used both externally and internally. They are specially applicable, and preferably to the other classes of diffusible stimulants, in those cases, enumerated in the general observations made upon diffusible stimulation, in which reaction must follow the state of prostration. In the collapse attendant upon severe injuries, and that which occurs at the commencement of febrile diseases, they are peculiarly indicated; because they have no special influence on the brain, and are not likely, therefore, as alcohol and some other cerebral stimulants, to affect that organ injuriously, when reaction takes place.

They are, in general, contraindicated by gastric inflammation, because brought into immediate contac with the inflamed part, and acting upon it with their whole stimulant power.

A great number of medicinal substances have the property of stimulating the circulation. Not to mention the nervous and cerebral stimulants, which, in accordance with their very definition, have this power, and, in some instances, in a very high degree, there are many others distributed among the various classes. But all of these have other properties which serve to place them elsewhere, and for which they are chiefly employed as medicines; and, though their action upon the heart and arteries may sometimes be incidentally useful, they are seldom or never employed with an exclusive view to this effect. The aromatics approach nearest in their properties to this class; but they are much more powerful as local than as general stimulants; and their application, as internal remedies, is almost restricted to affections of the alimentary canal. Mustard, copaiba, guaiac, mezereon, cantharides, savine, and many others, more or less excite the circulation; but each one of them belongs to some other class, as the emetics, diuretics, diaphoretics, emmenagogues, or alteratives; and they are almost never given as arterial stimulants simply.

The medicines strictly belonging to this class are very few, and might, perhaps, be still further limited; for carbonate of ammonia, which I attach to it, has, in addition to its influence over the heart and arteries, an action upon the nervous system, which would almost entitle it to a place among the nervous stimulants.