This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
It is this universality of their action that distinguishes them from the following class, or that of cerebral stimulants. As one of the nervous stimulants may superadd to its own characteristic property that of the arterial stimulants, so may it also possess additionally the peculiar influence of the cerebral stimulants, only that its own action would in that case be swallowed up or overwhelmed in this more powerful influence; and such really appears to be the case with some of the nervous stimulants. Thus, while assafetida, valerian, coffee, tea, etc., can scarcely be made To evince, in any quantity, or by any mode of administration, a peculiar tendency to operate on the cerebral centres beyond others, some medicines, much used and very efficient as nervous stimulants, if given more freely than is necessary for the exertion of their influence in this way, not only operate on the brain specially, but do so with great energy; as is the case with ether, camphor, and opium, which, in small doses, produce all the effects of the present class. The only difference between these two sets of nervous stimulants is that, while both, in certain doses, stimulate equably the general nervous system, the former cannot be made to operate specially on the brain, and the latter can be made so to act by simply increasing the dose; that is, in small doses they appear to operate diffusively and equably, and in larger, besides this general impression, superadd a special one upon the brain, which quite covers, if it does not supersede the first. In order to avoid unnecessary repetition, I shall treat of these latter remedies exclusively with the cerebral stimulants; as their most important therapeutic uses would attach them to that class; and it will be easy to point out their applications as nervous stimulants, when they are considered individually. Ether, camphor, and opium, therefore, will be found among the medicines of the next class.
The medicines here denominated nervous stimulants are generally called antispasmodics in therapeutic treatises, in consequence of the property of relaxing spasm, which they certainly possess under favourable circumstances, in a very high degree. But spasm depends on so many causes, and is associated, as an effect, with so many different pathological conditions, that the number of remedies applicable to its relief would scarcely fall short of the whole therapeutic catalogue. Dependent often upon inflammation, it may be treated advantageously by all the means which prove useful in the latter affection; that is, by most of the evacuants, revulsives, sedatives, and alteratives; in other instances, having its origin in debility, it will yield to astringents, tonics, and stimulants; and, in a third set of cases, being excited or sustained by various diseases in the different organs and functions, it must be encountered by. measures calculated to restore the affected organ or function to health. Again, this class of medicines is by no means confined, in its therapeutic agency, to spasmodic diseases. It is equally effectual in numerous other nervous disorders, to which more particular reference will be made directly. The nervous stimulants are but a very small section of the great host of antispasmodics, while they are themselves much more than mere antispasmodics. The name, therefore, being, in one sense, much too comprehensive, and, in another, scarcely in a less degree too restricted, should be abandoned, with other titles of a similar therapeutic origin, as the antiphlogistics, antiscorbutics, antisyphilitics, etc., which it has been found impossible to retain in any well-considered pharmacological classification. I have proposed a name for the class which simply expresses one of their most prominent properties, and the one for which they are most used in medicine.