This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol2", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Emollients, as here considered, are substances capable of forming a soft, slightly adhesive mass, perfectly bland and unirritating, which, when applied to the skin, has the effect of softening and relaxing its tissue. I confess that there is no very distinct line of demarcation between this class and that of the demulcents; and one of the methods, by which the medicines belonging to it act usefully in disease, is that which characterizes the succeeding class of Protectives. Yet there are points of difference sufficient, I think, to justify a retention of these agents in a distinct and long recognized association. Thus, emollients, as here defined, have definite limits of action, and are exclusively external. Demulcents may be used to any extent upon the surface, and are frequently used internally. One of the main offices performed by the demulcents is to mingle with acrid substances, and diminish or obtund their acrimony. This office cannot be performed by the emollients. These have a deeper effect upon the tissues than the demulcents, which for the most part operate upon the surface of application exclusively. On the other hand, the emollients differ from the Protectives in the softening and relaxing effect produced by the moist or liquid matter incorporated with them, while they may be less efficient upon the mere principle of excluding the air, which they do but partially.
So far as they are a distinct class of remedial substances, the emollients are merely the recipients of the fluids, which are the real agents in all the dynamic results produced. Thus, flaxseed meal is an emollient; but it is the liquid that may be mixed with it which really produces the effects. There are only two liquids which have this property; water, namely, and glycerin. The fixed oils often form a part of the emollient application, calculated to give it the due consistence, and therefore belong to the class; but the oils alone are inadequate to the effects aimed at. No one would expect the influence exercised by emollients, from a mixture of one of the fixed oils with sawdust. Water is almost always the active principle; and the substances here called emollients merely afford the means of applying it in the required method. Glycerin has probably the same Or very similar powers with water; but experience has not determined the point definitively.
Tho emollients are employed in the form of poultice or cataplasm. Water, by means of them, is confined within certain limits, at the temperature of the body, and is steadily thus applied, for a considerable length of time, so as to be able endosmotically to penetrate the tissues, and to an indefinite depth. The water, thus present in the tissues, in excess, exercises its sedative influence upon them, reduces their vital force, and diminishes their action. Perhaps its presence between the molecules, by somewhat separating them, lessens their vital cohesion by a kind of mechanical influence. But, however the effect may be produced, it is the water that produces it. The fixed oils are incapable of thus acting. They cannot sufficiently penetrate the tissues.
Under the operation of one of these emollients, the parts beneath often swell considerably, and become obviously soft and flaccid to the touch. if applied over a wounded or abraded surface, by a long continuance, they will often produce so flabby a condition as to favour the growth of fungous granulations.
As therapeutic agents, they are used chiefly, if not exclusively, in inflammation or vascular irritation; and they prove curative in these cases mainly by their sedative agency. if the inflammation of parts beneath has advanced to a certain stage, they often hasten suppuration. This they do simply by diminishing the vital force in the inflamed part, in consequence of which the exuded fibrin, instead of undergoing organization, perishes, and is converted into pus. By thus promoting the formation of abscesses, they often hasten the cure. But, in the earlier stage, or when the violence of the inflammation falls short of the suppurating point, they favour its resolution by direct sedation. in mere vascular irritation, which has not yet amounted to inflammation, they will be even more influential. Hence the use of emollient poultices in all superficial inflammations, whether idiopathic, or the result of a wound, or any other kind of injury. Their action extends also to the subcutaneous tissue. Hence their universal employment in boils and phlegmons. The inflamed lymphatic glands feel the same influence; as also do the arteries, veins, and absorbents of the extremities. The secreting glands outside of the great cavities are equally benefited. Emollient poultices, in inflammation of the testicles, and of the salivary glands, often produce the most happy antiphlogistic effects.
But what shall we say of their influence over inflammation of the tissues within the cavities ? I agree with those who believe that they are very efficient auxiliaries to other antiphlogistic remedies, in these cases, at least in many of them. in pleurisy, peritonitis, enteritis, gastritis, dysentery, and bronchitis, I believe they exercise very happy effects. But they must be very large, retained steadily for days, and frequently renewed so as to be always kept moist. Thus, in peritonitis and enteritis, the whole anterior surface of the abdomen should be covered. I can conceive that, in these cases, the water may enter the vessels and dilute the whole blood, by affecting that which is circulating through the vessels beneath. I have no doubt that pediluvia do act upon this principle to a considerable extent; and so may poultices. But that cannot be the main agency; as otherwise poultices to the extremities should have the same effect. Their influence in internal inflammations may be explained in two ways. The mucous surfaces sympathize with the skin, and may, when inflamed, feel a sedative influence exerted upon the surface of the body. As regards the serous tissues, which are in contact with the walls of the cavity, the water may possibly reach them from the surface, and thus act on them directly. in relation to inflammation of the parenchymatous tissues, I do not think the poultices are so effectual as in those of the membranes. Certainly, either of the explanations just given would not so well apply to them.