Volume 2

The household physician : a family guide to the preservation of health and to the domestic treatment of ailments and disease, with chapters on food and drugs and first aid in accidents and injuries / by J. McGregor-Robertson ; with an introduction by John G. McKendrick.

  • M'Gregor-Robertson, J. (Joseph), 1858-1925
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: The household physician : a family guide to the preservation of health and to the domestic treatment of ailments and disease, with chapters on food and drugs and first aid in accidents and injuries / by J. McGregor-Robertson ; with an introduction by John G. McKendrick. Source: Wellcome Collection.

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    glass tube which passes down the inside of the syphon, being often made of pewter, leads to this risk. The detection of lead in aerated water may be made in the way noted (on p. 648) for its detection in water. Mineral Waters.—These being medicines rather than beverages, are discussed in the part devoted to drugs. TEA, COFFEE, COCOA, CHOCOLATE, &c. Tea, cottee, cocoa, and many other substances used for the preparation of drinks, have several common features, of which it may be well to take gfeneral notice before considering each of the substances in detail. 1. They all contain an active principle, or alkaloid, containing nitrogen, akin to the active principle atropin, of the deadly nightshade (belladonna), akin to strychnine, to quinine, and to nicotine, the active principle of tobacco. In the case of tea this active principle is thein, in the case of coffee it is called caffein, and in the case of cocoa, theobromin, but the two former are apparently identical. 2. They all possess an aromatic oil, on which the flavour or aroma of the infusion depends. This oil does not exist in the substances in their fresh state, but is produced in the drying and roasting processes followed in their preparation for the market. 3. Tea and coffee contain an astringent sub- stance, tannin in the case of tea, and a modifi- cation of tannin in the case of coffee. It does not exist in cocoa, or at least is present only in very small quantity. 4. Besides these there exists a variety of sub- stances which are of no moment from the point of view of those who are considering their value as beverages, however interesting they may be to the analytical chemist. These substances are albuminoids, gum, dextrin, fat, wax, colouiing matters, woody fibre, and mineral matters. The active principle, aromatic oil, and astrin- gent substance are worth fuller consideration. Thein, or Caffein, for the two are identical, was discovered in coffee-berries in 1820. It had been previously discovered by Leeuwenhoeck, whose remarkable microscopic work has been referred to on p. 385, but had been afterwards overlooked. It is found not only in the coffee- bean but also in the leaf of the coffee-plant. In tea it was discovered in 1827, but it was not till eleven years later that the active principle of coffee, which had been called caffein, and that of tea, which had been called thein, were found to be one and the same substance. In 1841 the active }>rinciple of cocoa was discovered. It very much resembles thein. It is owing to the presence of this active jirinciple that all these substances possess their stimulating yiroperty. Other sub- stances used in a similar way to tea, coffee leaves, for example. Mate or Paraguay tea, and the kola-nut, also possess the same active prin- ciple as tea. “ It is remarkable,” says Attfield, who discovered the presence of thein in the kola-nut, “that the instinct of man, even in his savage state, should have led him to select, as the bases of common beverages, just the foui or five plants which out of many thousands a.re the only ones, so far as we know, containing thein.” Thein can be obtained in fine white needle- shaped crystals, and may be easily separated by anyone who cares to take a very little tiouble. Put a few finely-powdered leaves into the bot- tom of a clean cold test-tube, add a little water, and boil over a spirit-lamp till the water is nearly all driven oft. Add a pinch of diy mag- nesia, and mix with the leaves, with the aid of a glass rod, into a sort of paste. Then gently warm the bottom only of the tube in the flame of the spirit-lamp. The thein will be driven off and will be deposited on the upper cold part of the tube in fine needles, whei’e the naked eye will be able to perceive them, and a magnifying- glass will make them very distinct. The same process may be carried out in a tea-spoon over a c^as flame, a slip of cold glass being held over the spoon to condense the crystals. Thein has no smell but a slightly bitter taste. Its effects upon the healthy human body have been tested directly. In small doses it acceleiates the pulse and the breathing, and quickens ordi- nary muscular movements. It increases the action of the skin, and apparently also of the kidneys. It also excites the nervous system, quickening thought. In fact it produces in small doses those effects, the experience of which has led a cup of tea to be the unfailing resort as a cheering and gently-stimulating beveiage. It diminishes the tendency to sleep and removes some forms of headache. In large doses it acts as a poison, producing nervous excitement, trembling of hands and arms, and restlessness, and ultimately narcotic effects. A dose of 4 grains is fatal to a cat, nervous symptoms being prominent. A full tea-spoonful of tea would yield from 1 to 3 grains of thein—probably on an average about 2^ grains. Theobromin is chemically related to thein. Its