Persons of a gouty and rheumatic nature, above all, those prone to caleulous diseases of the lithic acid diathesis, find weak tea the least objectionable article of common drink. They should take it without sugar, and with very little milk. (Profit, ' On the Stomach,' p. 217.) Where the water is hard, the addition of a little carbonate of soda not only improves the tea, but renders it a more proper beverage for such persons. This addition of an alkali seems to increase the action of tea upon the skin, and to augment its cooling properties. Cream appears to lessen the action on the skin, as does also lemon-juice. (Smith, ut supra, p. 189.) Tea should not be used till about four hours after any solid meal.
The medical uses of tea are not many. In fevers it is not only an excellent diluent at the commencement, but a tincture of tea made by macerating tea in proof-spirit, and adding a teaspoonful of this to a small cup of water, and given at short intervals during the night, after the acute symptoms have subsided, is often of great service. For this purpose, in hospitals and workhouses, the leaves which have been used for the ordinary infusion may be macerated in alcohol, and a spirit of sufficient strength for this purpose obtained at a cheap rate.
In some forms of diseased heart tea proves a useful sedative. It is nearly as valuable an antidote to poisoning by opium as coffee is. Some cases of poisoning by arsenic and tartarised antimony have been pre vented proving fatal by the immediate administration of tea in the form of a very strong infusion. Here its power as an antidote depends upon its tannin decomposing the poisonous substances. (AsrruzioENrs.) But in poisoning by opium it is useful only in combating the secondary symptoms, and should not be administered till the stomach pump or other means have removed the opium from the stomach. Some eases of severe nervous headache are relieved by a cup of strong green tea, taken without milk or sugar. But this should be sparingly resorted to; it is a wiser plan to avoid the causes of such headaches. Tea has been looked upon as the great means by which intoxication was to be banished, but it is certain that to relieve the tremblings and other unpleasant effects of the abuse of tea, a little brandy or other alcoholic stimulant is occasionally added to the cup of tea, and so a habit is acquired which can never afterwards be relinquished.
Tea has frequently been denounced as a useless article of diet to the poor, as it is assumed to be devoid of nutriment, and the milk and sugar which are added are supposed to be the only beneficial ingredients. Dr. Lettsom has given a calculation, partly his own, and partly taken from 'Essays on Husbandry,' to show how much is, in his view, unnecessarily expended by them in this way. But the observations of
Liebig are thought to offer a satisfactory explanation of the cause of the great partiality of the poor not only for tea, but for tea of an expensive and therefore superior kind :— " To see how the action of caffeine, asparagine, theobromiue, may be explained, we must call to mind that the chief constituent of the bile contains only 3.8 per cent. of nitrogen, of which only the half, or P9 per cent., belongs to the taurine. Bile contains in its natural state water and solid matter, in the proportion of 90 parts by weight of the former to 10 of the latter. If we suppose these 10 parts by weight of solid matter to be choleic acid, with 3.87 per cent. of nitrogen, then 100 parts of fresh bile will contain 0.171 parts of nitrogen in the shape of taurine. Now this quantity is contained in parts of caffeine ; or grains of caffeine can give to an ounce of bile the nitrogen it contains 'in the form of taurine. If an infusion of tea contain no more than the of a grain of caffeine, still, if it con tribute in point of fact to the formation of bile, the action, even of such a quantity, cannot be looked upon as a nullity. Neither can it be denied, that in the case of an excess of non-azotised food and a deficiency of motion, which is required to cause tbe change of matter of the tissues, and thus to yield the nitrogenised product which enters into the composition of the bile ; that in such a condition the health may be benefited by the use of compounds which are capable of supply ing the place of the nitrogenised substance produced in the healthy state of the body, and essential to the production of an important element of respiration. In a chemical sense—and it is this alone which the preceding remarks are intended to show—caffeine, or theine, asparagine, and theobromine, are, in virtue of their composition, better adapted to this purpose than all other nitrogenised vegetable principles. The action of these substances, in ordinary circumstances, is not obvious, but it unquestionably exists. Tea and coffee were originally met with among nations whose diet is chiefly vegetable." (Liebig's Animal Chemistry,' p. 178.) These facts show in what way tea proves to the poor a substitute for animal food, and why females and literary persons who take little exercise manifest such partiality for it. `They also explain why the attempts, and they have been numerous, to find among other plants a substitute for tea have invariably failed of success.