Page:Popular Science Monthly Volume 29.djvu/78
THE POPULAR SCIENCE MONTHLY.
filter and simply pouring on the boiling water. In this way he thought to evade the presence of tannin in his tea. But if you try the experiment, and allow the product, as it runs through the filter, to fall into a solution of perchloride of iron, you will find that an intense inky-black coloration is produced, showing that tannin has come through in abundance.
In order to diminish as far as possible the retarding influence of tea on salivary digestion, it should be made weak and used sparingly, and it should not be taken icith but after the meal.
There is another means, mentioned by Sir W. Roberts, of obviating the retarding effect of tea on salivary digestion, and commended by him to the dyspeptic : it is to add a pinch of bicarbonate of soda to the tea when it is being infused in the tea-pot. He found that ten grains of soda added to an ounce of dry tea almost entirely removed this retarding influence. The infusion thus made is darker than usual, but the flavor is not sensibly altered, nor is the infusion rendered alka- line, for tea infusion is naturally slightly acid, and the soda, in the proportion mentioned, only just neutralizes this acidity.
Coffee, unless taken in very large quantity, has very little retarding effect on salivary digestion ; this is explained by the fact that the tannin of tea is replaced in coffee by a substance called caffeo-tannic acid. Cocoa resembles coffee, and has little or no effect on salivary digestion ; the use of coffee or cocoa is therefore preferable to that of tea for persons of feeble digestion.
With respect to the influence of tea and coffee on stomach diges- tion, it was found that they both exercised a remarkable retarding effect. There was no appreciable difference in the two beverages if they were of equal strength ; but, as coffee is usually made of greater percentage strength than tea, its effect must ordinarily be greater. Cocoa also had much the same effect if used of the same strength as tea or coffee, but, when of the strength ordinarily employed, its effect was inconsiderable. Strong coffee cafe noir had a very powerful retarding effect, and persons of weak digestion should avoid the cus- tomary cup of " black coffee " after dinner.
"I could not detect," says Sir W. Boberts, "any appreciable difference be- tween the effect of tea infused for two or three minutes and tea infused for fif- teen or thirty minutes. If you wish to minimize the retarding effects of tea in persons of weak digestion, you should give instructions that the beverage be made weak, or that it be used in sparing quantities." And he adds in a foot- note : "A good deal has been said of the injurious effects on gastric digestion of tannin contained in tea. I question whether the statements made with reference to this matter are worthy of attention. It has been alleged that meat-fiber is hardened by tea, and that the coats of the stomach are liable to be injured by this beverage. These views are entirely theoretical" (p. 48).
Perhaps one of the most unexpected results of these experiments of Sir W. Roberts was the discovery that beef-tea had a powerful retarding effect on peptic digestion, as much so as that of a five per