Called also Antacids and Absorbents, include Potash, Soda, Ammonia, Lime, and Magnesia, and their carbonates. The Carbonate of Lithia is also a powerful medicine of the same class. In their pure states, Potash, Ammonia, and Lime are sometimes employed as escharotics. The carbonate is the form in which they are generally administered internally. The following are some of the principal objects attained by their employment: -

As Antacids. It is in this character that alkalies are chiefly employed; and if given judiciously, they perform their office with certainty and rapidity; but if given indiscriminately, or in too large or too long-continued doses, they are productive of great mischief. Dr. Prout's observations on this point well merit attention. "Alkalies," he observes, "exert no curative effect, that is, they will not prevent acidity; on the contrary, when taken in large doses, and at improper times, the effect of alkalies is to cause an absolute increase of acid. Thus, when a large quantity of Alkali is taken into an empty stomach, the

* Bull. de Therap., 1851. Lectures on the Principles and Practice of Med., vol. ii. p. 653.

On Stomach and Renal Diseases, 4th Ed., p. 91, et seq.

immediate effect is, that the stomach, in endeavouring to resume its natural condition, throws out an additional quantity of acid to neutralize the redundant alkali. When alkaline remedies, therefore, are injudiciously persisted in, a daily contest arises between the stomach and the doctor. If the constitution be strong, the stomach usually gains the ascendency, but at the expense of extraordinary labour in the secretion of a greater quantity of acid. If, on the contrary, the stomach be weak, the doctor may conquer, but at the risk of still further enfeebling the vital power of that organ; and in both instances the general result will be that the diseased functions of the stomach will be augmented rather than improved. The beneficial effect of alkaline remedies is confined to the neutralization of the acids already formed, thus preventing their secondary effect on the system." To the above valuable remarks it may be added, that a certain amount of acid is necessary to carry on the digestive process, and that by the free use of Alkalies we neutralize, not only the superabundant, but the necessary amount of acid, thus establishing a state worse than the first. It may be stated in general terms that the person who habituates himself to the use of Alkalies will, in a shorter or longer time, be the subject of the most obstinate forms of Dyspepsia. Other ill consequences follow the injudicious use of Alkalies: they apparently alter the quality of the blood, destroy the cohesive property of the blood-corpuscles, render the fibrin less plastic, induce a thin and liquid state of the circulating fluid, petechia) appear on various parts of the body; the patient perspires profusely, becomes low-spirited and emaciated, and less capable than when in health of physical exertion; the assimilating functions are deranged, and serious disorder of the nervous system results. In some habits, Alkalies occasion a deposit of phosphates in the urine. Magnesia produces these effects less rapidly than the other Alkalies.

2891. When Alkalies are given with a view of correcting acidity of the primAe viae, they should not be given immediately after a meal, as they would interfere with the digestive process, but in about three or four hours afterwards, when the digestion of the last meal may be supposed to be about completed. Vegetable bitter infusions should not be employed as a vehicle, as they neutralize or destroy, according to Dr. Prout, the antacid properties. If the acidity be confined to the lower portions of the intestinal canal, the more insoluble antacids, as Magnesia, are preferable to Potash, and the more soluble carbonates. There are some individuals who cannot take Alkalies in any form, however strongly their use appears to be indicated. In some they produce great excitement, particularly of the nervous system and of the cerebral functions. Dr. Prout mentions many such cases. In others, when Alkalies cannot be tolerated in a free or carbonated state, they can often be taken in conjunction with a vegetable acid; and in others, the addition of Ammonia will cause them to be borne. Potash disagrees with some persons who can take Soda or Magnesia with impunity.* When Alkalies are given with a view of obtaining their diuretic effect, they should be combined with Acetic or some other vegetable acid, and administered largely diluted.

2892. As a means of rendering Acid Urine Alkaline, this class of remedies is much employed. Liquor PotassAe, the Carbonates and the Salts of Potash, with vegetable Acids (e. g., the Acetate and Citrate), are most frequently prescribed for this purpose. The causticity of Liquor PotassAe interferes with its administration in doses sufficiently large to render highly acid urine alkaline; otherwise it is particularly eligible, as it is believed to diminish ardor urinAe, and to allay vesical irritation, which frequently accompany an acid state of the urine. The Acetate, Citrate, and Tartrate of Potash are decomposed in the system, and are converted into carbonates. The corresponding preparations of Soda may be employed for the same purpose; but it is held by many that the action of Soda is rather directed to the liver and its secretion, whilst Potash is believed to act more energetically on the kidneys. The Urate of Potash, also, being much more soluble than the Urate of Soda, the former alkali is preferable when an excess of Uric Acid is present in the urine. According to Garrod, the Carbonate of Lithia exerts a more powerful effect in rendering the urine alkaline than do the corresponding salts of Soda and Potash. The Salts of Ammonia, with a vegetable acid, exert no influence in producing an alkaline condition of the urine.§ Dr. Owen Pees || suggests the administration of Alkalies when the urine is highly alkaline. He observes that there are some cases in which the urine may be supposed to be acid on its leaving the kidneys, but by its irritation of the internal surfaces of the ureters and bladder, to produce so copious a secretion from them of alkaline mucus, as to cause the acidity to be more than neutralized, and the urine to be rendered alkaline with phosphatic deposits. Acting upon this view, Dr. Pees administered Alkalies in numerous cases, and the result fully corroborated the correctness of the theory. The remedy should be given in small doses. The influence of Alkalies in checking the production of Artificial Diabetes has been ably shown in the important researches of Dr. Pavy. ¶ The investigation is well worthy of further research.