human
The peculiar effects of tea and coffee are due to the alkaloid. These effects are of a _refreshing_ character. The circulation of the blood is increased; the elimination of CO_{2} by the lungs is heightened. The reflex excitability of the nerve centres is roused, thereby increasing the impressionability of the consumer, and great wakefulness results; it also excites the peristalsis of the intestines. Tea and coffee, then, are stimulants; they rouse the tissues to increased action, make us insensible to fatigue, and enable us to do more work than we otherwise could. The differences between these stimulants and alcoholic stimulants are worth noticing. Tea and coffee keep us awake and attentive; and those who have taken either for the purposes of midnight study, will know how under their influence the receptive powers of the brain seem to be at its maximum. They cause no mental 'elevation,' and do not rouse the imaginative faculties as a glass of wine seems to do. They enable a man to work, and often rob him of sleep, and do not, like a glass of wine, tend to increase the power of sleep after the work has been accomplished. The tannic acid in tea is doubtless one of the causes why it is as a drink so attractive. It is slightly astringent, and clean in the mouth, and does not 'cloy the palate,' an expression for which I can find no scientific equivalent; tannic acid is also one of the dangers and drawbacks of tea. It is largely present in the common teas used by the poor.... Excessive tea-drinkers are more common than excessive coffee-drinkers, because the heavier coffee more easily produces satiety than the lighter tea; and it is not possible for ordinary stomachs to tolerate more than a certain amount of coffee, even when pure, and only a very small amount of the thick, sweet, adulterated stuff which too often passes for coffee in this country.... Tea is more of a pure beverage than coffee, has less dietetic value, and is less stimulating; it is more capable of being used as a pure luxury (it is indeed the tobacco of women), but its great astringency is one reason which makes its excessive use highly undesirable.
gpt
Without its aid, he says,
human
I should be idle.