These are characterized by bitterness with little or no intermixture of other taste, and by a purely tonic power, which is identical or nearly so in all. There appears to be a close relation between the bitter and tonic properties; so much so, that the possession of the former may be considered as prima facie evidence of the possession of the latter also. Cullen, indeed, believed this connection to be essential, and taught that it was the tonic power of bodies that gave them bitterness. Bitter substances might have other powers in addition, such as the narcotic and purgative, which might prevent their use in reference to their tonic property, but they still possessed it. He even seems to have thought that the bitterness might reside in a single principle of peculiar composition. This, however, has been shown not to be true. A great number of proximate bitter principles have been discovered, very different in offensive cod-liver oil; but this might injuriously affect the influence of the medicine by adding its own sedative action. Not more than one-quarter or at most one-half of the quantity would be admissible; and the smaller close would probably be sufficient for any ordinary oil. M. Jeannel, however, thinks that the best agent for the purpose is cherry-laurel water; and it is sufficient to shake the oil with its volume or at most twice its volume of the distilled liquid. The effect is in either case owing to the hydrocyanic acid present: and I have no doubt that the wild-cherry bark tea, referred to in the text, acts in the same way. (Journ de Pharm. et de Chim., 3e ser., xxxviii. 360).

In cases in which, though swallowed, the oil is soon afterwards rejected by vomit ing, M. Vigla asserts that he has uniformly found this effect to be obviated by administering to the patient, after he has swallowed the medicine, eight or ten grains of calcined magnesia. (Ibid., 3e ser., xli. 248).

Extract of Cod-liver. A preparation claiming to be an extract of cod-liver, and which, on chemical examination, has been found to contain all the principles of the oil, excepting oily matter and glycerin, has been brought before the notice of the profession as a substitute for the oil. But too little is yet known of it to justify its adoption among officinal remedies (Chem. News, Jan. 5, 1866, p. 10.) - Notes to the third edition.

composition and chemical relations. Yet I am inclined to think that there is some ground for the opinion of the identity of the two properties. It is easy to conceive that the same arrangement or shape of particles which causes the impression of bitterness on the organs of taste, may give rise to the tonic impression upon the stomach; and that, though all bitters may not seem to be tonic, this may be owing, not to the want of the property, but to the possession of other powers of affecting the system, so influential as completely to overwhelm and conceal it. Nux vomica is tonic in small doses; but, largely given, produces a peculiar effect on the nervous system which quite obscures the tonic. Even quinia, in very large doses, loses apparently all its tonic powers, in its overwhelming influence upon the nervous centres. The same may be the case with other bitters of great medicinal energy, such as colo-cynthin, elaterin, digitalin, morphia, etc. If reduced in their dose so as. to be unable to produce their more powerful and characteristic effect, it is very possible that they might prove tonic to the digestive organs.

Effects on the System

The effects of the simple bitters are to increase the appetite, invigorate digestion, and moderately to exalt the nutritive function. They have little direct influence on the circulation, and perhaps none upon the nervous system. The proper cerebral functions do not appear to be affected by them in any degree, unless in so far as these may be influenced by the condition of the others mentioned. Their main operation is directly upon the mucous surface of the alimentary canal; and their general tonic effects may be ascribed chiefly to the increased quantity, and improved quality of the blood, resulting from the stimulated digestion. It is probable that a stimulant effect is extended sympathetically from the gastro-intestinal surface to the liver and pancreas, upon the same principle as that by which the presence of chyme in the duodenum excites these organs. It is possible that the bitter principles may be absorbed, and, through the circulation, act on the nutritive function everywhere; but this has not been proved in relation to the set of substances now under consideration. One evidence that their direct operation is mainly upon the digestive organs is offered by the fact, that, when they are taken largely, so as to prove irritant, their increased effects are exhibited in those organs, and not directly elsewhere. The simple bitters are apt, in over-doses, to prove laxative, and sometimes nauseate and even vomit; but they do not disturb the heart, nor the cerebrospinal system, nor any other part of the body, unless in so far as these may feel the condition of the digestive organs.

Therapeutic Application

The simple bitters are especially applicable to cases in which the indication is to promote the digestive function. In pure dyspepsia, they are, upon the whole, the best tonic remedies in our possession. By moderately stimulating the stomach, they probably favour the secretion of a healthy gastric juice, capable of dissolving the food, and thus obviate the stomachic uneasiness, flatulence, and sour or acrid eructations, resulting from the irritation of undigested matters, of substances generated by the chemical reaction of these matters, and probably also of the unhealthy secretions of the weakened stomach itself. They extend a similar stimulant influence to the torpid bowels, and probably also to the torpid liver, thus still further favouring the digestive function. Even in deficient action of the bowels and of the liver, unattended with symptoms of proper dyspepsia, they are often useful, particularly in combination with remedies more especially addressed to those functions. Hence their use as adjuvants to laxatives in constipation, and to cholagogues in jaundice depending on hepatic torpor. From their usefulness in debility of digestion, it follows that good may be expected from them in all those disorders of sensation and function having their root in this affection. Hence, they are among the most efficacious remedies in headache, vertigo, and other deranged cephalic sensations, connected with excess of acid in the stomach; in which cases they should be given combined with an antacid, as magnesia when there is costiveness, chalk when there is diarrhoea, the alkaline carbonates or bicarbonates when there is neither, and aromatic spirit of ammonia when there is great gastric insensibility.

The simple bitters are also well adapted to the debility of convalescence from acute diseases, whether general, as fevers, or local, as cholera, dysentery, and other affections of the alimentary canal. Whenever, under these circumstances, the original disease has been removed, and the appetite remains feeble, and the digestive powers insufficient for the management even of the food that may be taken, the gentle stimulation of the simple bitters is indicated, and will often contribute to the restoration of health.

In all cases of general debility, and of impaired blood, originating in or connected with simple weakness of the digestive function, these medicines may be used with the hope of benefit; and they are often profitably combined with other tonics, which exercise a more powerful direct influence over the system at large.

They were formerly employed in intermittent and remittent fevers; being administered, in the absence or decline of the fever, as antiperio-. and were supposed to be peculiarly applicable to cases in which the apyrexia was not sufficiently complete for the use of Peruvian bark. But, since the discovery of quinia, this use of the simple bitters has been in great measure abandoned.

They have been supposed to possess anthelmintic properties; and are no doubt occasionally useful in verminose cases. Some have supposed them to operate by poisoning the worms; and experiment has shown that some of them are noxious to inferior animals; but the probability is, that they do good much more by giving proper tone to the bowels, and thus removing the condition favourable to the development of the worms, than by a direct action on the parasites themselves.

They are more frequently given as adjuvants of other medicines than by themselves. They are indicated, in this way, whenever weakness of the digestive function is complicated with the special disease prescribed for. Reference has already been made to their combination with laxatives in constipation, with the mercurial preparations in jaundice, or other cases of torpid liver, and with other tonics in general debility, as with the chalybeates in anaemia. In the various nervous affections, they are often useful in conjunction with the metallic tonics and the nervous stimulants, in dropsy with diuretics, and in amenorrhoea with emmena-gogues. The different forms in which they are prepared, as those of powder, extract, infusion, and tincture, afford facilities for these combinations, which should not be overlooked in prescription. When given in chief, they are themselves often aided by the addition of aromatics, as of ginger, orange-peel, etc., which render them more stimulant to the stomach when very languid, and more easily retained by it when irritable.

The different simple bitters are so similar in their effects, that they may be given indiscriminately; one being preferred to another according to convenience, the choice of the patient, or the existence of some idiosyncrasy which may render any one or more of them inadmissible.