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.
This subdivision of medicines is characterized by an agreeable odour and taste, dependent on the presence of volatile oil. They do not correspond exactly with the tonics, being more excitant, though less so than the class of circulatory stimulants. They do not equal the bitter tonics in the property of promoting the digestive and nutritive functions. Their action, moreover, is more speedy, and less durable. Yet they approach more closely to these medicines than to any other division in the classification I have adopted, and are often used, in conjunction with tonics, to increase their stimulant influence, or in other ways modify their action. I have, therefore, thought it best to follow the example of Dr. J. Murray, of Edinburgh, in his excellent system of Materia Medica, in arranging them in the position they here hold; guarding the student, however, against the mistake of supposing them identical, or even very analogous, in their operation, with the bitters.
When taken internally, the aromatics occasion generally an agreeable feeling of warmth in the stomach, moderately increase the frequency of pulse and heat of the surface, and often diffuse a pleasant glow over the system, without exhibiting any special tendency towards the brain or nervous system generally, or any particular influence over the secretions. They resemble, in their direction to the circulatory function, the medicines hereafter to be described under the name of arterial stimulants; but they differ, in being much more powerful, relatively, in their local than their general excitant effect. Thus, to whatever surface they are directly applied, whether the skin, the mouth and fauces, or the mucous membrane of the stomach, they stimulate actively the blood-vessels of the part, and, largely used, cause high vascular irritation, or even inflammation; while upon the heart and general circulation they produce little greater effect than might be ascribed to sympathy with the local excitement. This disproportion in their local stimulation may be ascribed to the difficult absorption of the volatile oils, to which they owe their powers. There is a great difference in the absorbability of the different volatile oils. Some, as those of turpentine, copaiba, garlic, etc., enter the circulation with great facility, and hence display considerable energy in their action upon the system generally, or on organs remote from the point of their application. The aromatic oils, as those of cinnamon, cloves, ginger peppermint, etc., have, in general, much less of this facility; and, though they may act locally with equal power, are much less diffusible in their effects.
In their operation specially upon the stomach and other portions of the alimentary canal, they do not so much invigorate the particular function of digestion, as produce a general vascular excitement of the parts, attended with a comfortable or pleasurable sensation, comparable to that of a genial glow on the surface of the body. In the accompanying plentiful, but not excessive supply of blood, which is the proper material for all the functions, that of the stomach is in a state to respond to its special stimulants; and tonics, therefore, will often operate with greater energy, in connection with aromatics, than when administered alone. The muscular tissue, too, without being stimulated, as by purgatives, to an increase of its regular peristaltic action, is yet put into a condition of greater power, and will contract with increased energy under the special stimulus of distension, or with a better regulated movement under that of cathartic medicine. Upon these principles may be explained all the peculiar therapeutic uses of the aromatics.