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.
These are remedies which directly depress the vital functions. While a few operate universally, as cold and water, most of them, like the corresponding stimulants, act especially or exclusively on one of the two great systems, the circulatory, namely, and the nervous; some prominently affecting the former, and therefore denominated arterial sedatives, others the latter, and named cerebro-nervous sedatives.
1. Arterial Sedatives constitute one of the ultimate classes. They act mainly, if not exclusively, in their primary influence, upon the heart and arteries, without any direct effect on the cerebro-spinal functions. As, among the results of the circulatory depression, is a reduction also of the temperature, they are frequently called refrigerants.
2. CErebro-spinal Sedatives. These may be advantageously divided, like the corresponding subdivision of stimulants, into the nervous, cerebral, and spinal, which form ultimate classes.
a. Nervous Sedatives are such as reduce generally the nervous functions, without any special reference to the brain. They uniformly, either by a conjoint primary action, or secondarily through their influ-ence on the nerves, reduce the force of the circulation also. They are usually designated as sedative narcotics.
b. Cerebral Sedatives are remedies which, while they depress the circulation either primarily or secondarily, exert a special and marked influence, of a sedative character, on the cerebral functions. Like the preceding class, they would rank with the medicines usually known as sedative narcotics.
c. Spinal Sedatives act by directly depressing the special functions of the spina] marrow, including of course its reflex action, with little if any direct influence on the brain.