Universal experience teaches us that tea exhilarates without intoxicating, stimulates the circulation, excites the brain to increased activity, promotes wakefulness, and banishes the sense of weariness. It also deadens the sensation of hunger, and increases the power of fasting. It will cool the body when hot, and warm it when cold. In tropical countries it has been found to be a most valuable restorative when taken by soldiers on long and fatiguing marches. Lord Wolseley, who is a great advocate for tea as a beverage on which to do hard work gave orders that the water-bottles of the soldiers whom he led on the two famous and exhausting expeditions of the Red River, and up the Nile to Khartoum, should be filled with cold tea; and he is convinced that, whereas alcohol induces fatigue, tea will give the power to endure and overcome it.

The exhilarating and the staying powers of tea are due respectively to the theine and tannin it contains; the theine exhilarates the nervous system, the tannin stays hunger. This latter point has been made clear by the interesting and valuable experiments of Sir William Roberts, who has shown that tannin, taken even in very small quantities, has an inhibitory or slowing influence on the digestion of food in the stomach. He found that this took place with tea made at the ordinary strength, and taken in the usual amount, with food; the digestion being still longer delayed if a large amount of fluid tea was drunk. He could not, however, detect any appreciable difference between the, inhibitory effect of tea infused for two or three minutes and tea infused for fifteen or thirty minutes. In fact, the tannin, always and inevitably present in tea, is sufficient to retard digestion; and the amount of tannin taken, and the increased retarding effect produced, depend not upon the length of time the tea is infused, but upon the total quantity of fluid tea drunk. This inhibitory or retarding influence of tea on digestion Sir William Roberts considers to be useful and salutary. Slow digestion does not mean imperfect digestion; and it would appear that the tannin by slowing digestion, and the theine by exhilarating the nervous system, give to tea the extraordinary power of inducing the endurance of fatigue and fasting, of which we all have daily experience, and which makes tea so favourite a beverage with the poor. The afternoon cup of tea, taken with a small amount of bread and butter, will enable a great many hard workers to dispense with luncheon, and to remain without food till a late dinner-hour, without experiencing any discomfort. The inhibitory or slowing influence of tannin is more marked on starch than on albuminates; hence the satisfying character of a good meal of tea and bread, and the probable cause of indigestion and nightmares consequent on a " high tea " with cold pie and cakes. A pinch of bicarbonate of soda put into the teapot will destroy the deterrent effect of tea on stomach digestion (Roberts).

Tea has its dangers, and these are well known to doctors. If taken in excess, it may produce cardiac disturbances, palpitations, flutterings, a nervous impression of distress and anxiety, and even intermittence of the pulse and sleeplessness, while sometimes it provokes an obstinate form of gastric catarrh. It is said that these effects are due to the tannin contained in the tea, but this assertion is by no means proved. Tannin has but a slight effect on peptic action, and the slowing effect of tea upon stomach digestion is not fully explained by the presence of tannin in tea (Roberts). The assertion one hears made that the tannin of tea tans the coats of the stomach into leather is one of those statements which are based more upon a lively imagination than on the data of science. The coats of the stomach do not in any way resemble a hide. They are, moreover, not dead membrane, but living tissue, and the effect of tea on meat fibre is not to harden it, but to cause it to swell. If tea is found to disagree with a person either by over-stimulating the nervous system, or by delaying digestion, the remedy is to take it in smaller quantities or extremely weak, and also not with but after food. In some forms of dyspepsia, particularly in the hysterical flatulent form, tea should, at all events for a time, be entirely abstained from.