When pure astringency is required, tannic acid is preferable to the crude medicines containing it, from its comparatively small dose, its less unpleasant taste, its less liability to offend the stomach, and from the circumstance that, not being associated with principles having a different action from its own, it can be given in cases in which the crude medicine, in consequence of containing such principles, may be contraindicated.

1. Internally, it may be used most advantageously in affections of the stomach and bowels, with the inner surface of which it comes into direct contact. In all cases of diarrhoea and chronic dysentery, demanding the use of astringents, especially in the former of these diseases, it is very useful. It may even be employed in these affections, in some instances, when the medicines containing it could not, in consequence of associating too much of a tonic or stimulating property with their astringency. In cholera infantum it may frequently be associated usefully with the other medicines employed. It is asserted to have produced extraordinary effects in epidemic cholera, in which it may be given at any stage so long as copious evacuations continue. From the rapidity and violence of this disease, it must be used more largely than in most other affections; from five to ten grains being required, to be repeated every half hour or hour until the discharges are checked. In hemorrhage from the stomach and bowels, not connected with high vascular irritation or acute inflammation, it is an excellent remedy. In haematemesis it should be given preferably in solution, as it will thus act more promptly and equably upon the bleeding surface. In intestinal hemorrhage, on the contrary, the pilular form is to be preferred, because, in this state, the medicine will be more likely to pass through the stomach unaltered, and thus reach the seat of its destined action. In all these affections, it should generally be combined with opium, and often also with ipecacuanha, the proportions of which should vary to suit the particular circumstances of the case. Acetate of lead is generally indicated at the same time. Should this and the tannic acid have been employed separately without success, they may be given conjointly; for, though the tannate of lead would be formed, yet there is reason to suppose that this might prove more efficacious, in certain cases, especially in the intestinal affection, than either of the two medicines alone.

Though less efficacious in complaints the seat of which it cannot directly reach, tannic acid has yet been highly recommended, as an internal remedy, in various morbid discharges, whether secretory or hemorrhagic, proceeding from other sources than the alimentary canal. Profuse and exhausting expectoration, whether mucous or purulent, colliquative sweats, excessive diuresis, chronic catarrh of the bladder, haemoptysis, haematuria, and menorrhagia, are the affections of this kind in which it has been used. But in all of them I should prefer the mineral astringents; and the probability is that gallic acid might prove little less effective than the tannic. It is said, given to the extent of nine grains daily, to have proved very serviceable in cases of purulent infection or pyaemia, in which sulphate of quinia was thought to have acted injuriously. {Med. T. and Gaz., Aug. 1862, p. 149).

Dr. S. Scott Alison recommends the acid as an excellent remedy in dyspepsia, in which he states that it promotes the appetite, relieves flatulence, and not unfrequently, instead of constipating, produces a healthy action of the bowels. It would probably prove not less efficacious than galls, in obstinate flatulence and tympanites dependent on relaxation of the bowel. It is asserted to have been very successful in the cure of intermillents, and has been given as an anthelmintic, in the dose for children of from five to ten grains. It has been strongly recommended in dropsy with albuminous urine, in the quantity of from thirty grains to a drachm in twenty-four hours. (Arch. Gen., Janv. 1850, p. 35.) Tannic acid has also, like galls, been recommended as an antidote to the poisonous vegetable alkaloids, and certain metallic salts, especially tartar emetic; but, for reasons already mentioned, it should not be relied on to the exclusion of other measures. (See pages 112-3).