CHAMBERS'S INFORMATION FOR THE PEOPLE. 



cent, chlorine and 40 sodium. The salt of com- 

 merce, however, is never found absolutely pure, 

 being less or more contaminated with salts of 

 lime and magnesia, as well as insoluble matter. 

 Thus an average of foreign bay-salts yielded to 

 analysis 3^ per cent of such impurities ; British 

 salt from sea-water, upwards of 4 per cent. ; and 

 that from English rock-salt, somewhat more than 

 i per cent. The purer salt is, of course the more 

 wholesome will it be as an article of diet, and the 

 more effectual for the purposes of pickling and 

 curing provisions. 



BEVERAGES. 



Writers on dietetics are in the habit of classify- 

 ing drinks or beverages according to their sensible, 

 chemical, or medicinal properties. Thus we have 



1. Mucilaginous, farinaceous, or saccharine drinks ; 



2. Emulsive or milky drinks ; 3. Animal broths, 

 or drinks containing gelatine and osmazome ; 4. 

 Aromatic drinks ; 5. Acidulous drinks ; and, 6. 

 Alcoholic and other intoxicating drinks. Water, 

 however, is the only true natural beverage ; it 

 forms the basis of the whole of the above the 

 other constituents being merely solid or liquid 

 substances mixed with or dissolved in it. Being 

 reduced to a condition of minute subdivision, 

 the alimentary action or effect of such of these 

 substances as possess a dietetic value is much 

 facilitated, and thus, in point of easy assimilation, 

 beverages are immensely superior to solid food. 

 We shall now briefly allude to the more abundant 

 and familiar beverages. 



1. The mucilaginous, farinaceous, and saccharine 

 drinks are perhaps the simplest, next to water. 

 They are merely solutions, infusions, or decoctions 

 of substances already described, and are known 

 by such terms as glim-water, toast-water, sugar- 

 water, barley-water, mucilage of rice, and gruel 

 from oats, sago, arrow-root, or tapioca. They are 

 all very slightly nutritive ; and are used chiefly in 

 the sick-chamber as demulcents and diluents. 



2. Emulsive or milky drinks are such as hold 

 in suspension any oily or fatty substance in a 

 finely divided state. Animal milk (already de- 

 scribed) is at the head of this section. 



3. Broths and soups, or drinks containing gela- 

 tine, creatine, creatinine, inosite, osmazome, &c. 

 are usually prepared from beef, mutton, veal, and 

 chicken. As in the case of extract of beef, their 

 nutritive properties depend chiefly upon the crea- 

 tine and allied principles contained in them, for 

 no satisfactory evidence exists regarding the value 

 of gelatine as a food. It is not unlikely, however, 

 that this substance assists in forming the gelati- 

 nous tissues, and that it also, like albumen, gene- 

 rates force by its oxidation in the body. Meat of 

 good quality yields to boiling water, creatine, crea- 

 tinine, and similar principles, osmazome, gelatine, 

 fatty matter, some salts and water; and to prepare 

 a soup so that none of these may be dissipated 

 and lost, is the chief point requiring attention. 

 When pot vegetables, as turnips, carrots, onions, 

 barley, &c. are used, of course these communicate 

 new principles to the liquid as mucilage, sugar, 

 azotised products, volatile oil, and salts. 



4. Of the aromatic drinks, tea, coffee, and choco- 

 late are pre-eminently the most familiar. 'We shall 



750 



never, certainly, be able to discover,' writes Baron 

 Liebig, ' how men were led to the use of the hot 

 infusion of the leaves of a certain shrub (tea), or of 

 a decoction of certain roasted berries (coffee). 

 Some cause there must be, which would explain 

 how the practice has become a necessary of life to 

 whole nations. But it is surely still more remark- 

 able that the beneficial effects of both plants on 

 the health must be ascribed to one and the same 

 substance, the presence of which in two vegetables 

 belonging to different natural families, and the 

 produce of different quarters of the globe, could 

 hardly have presented itself to the boldest imag- 

 ination. Yet recent researches have shewn, in 

 such a manner as to exclude all doubt, that caffciit, 

 the peculiar principle of coffee, and thein, that of 

 tea, are in all respects identical.' The fact is cer- 

 tainly striking enough, and all the more so that 

 cocoa or chocolate, mate* or the tea of Paraguay, 

 and guarana, the common beverage of the native 

 tribes in the neighbourhood of the Amazon, also 

 yield principles identical with thein and caffein. 



Tea was presented, in 1664, as a rare and pre- 

 cious gift, to the queen of England, and now 

 it forms an almost essential article of consump- 

 tion in the poorest households of the kingdom. 

 From a recent official account, it appears that in 

 1871, the enormous quantity of 123,401,889 Ibs. 

 or over 55,090 tons was used in this country, or 

 about 3^ Ibs. during the year by each individual. 

 The greatest quantity is obtained from China, 

 but ever-increasing supplies are derived from 

 Assam and Cachar in Hindustan. The botanical 

 source of tea is a plant named Thea sinetisis, of 

 which two varieties are distinguished, T. viridis 

 and T. Bohea, from either of which green or 

 black teas may be produced. Of the green teas, 

 there may be mentioned, in their order of quality 

 and expensiveness Young Hyson, Gunpowder, 

 Hyson, Imperial, and Twankay ; and of the black 

 teas, in the same order Flowery Pekoe, Orange 

 Pekoe, Pekoe, Souchong, and Congou. When 

 analysed, they all yield chlorophyl or colouring- 

 matter, wax, resin, gum, albumen, lignin, extract- 

 ive matter, tannin, empyreumatic volatile oil, and 

 thein. The important and valuable properties 

 of tea seem to depend on the last two of these 

 substances, although decided effects are likewise 

 caused by the tannin. The volatile oil is not pres- 

 ent in the fresh leaves, but is produced by decom- 

 position of some of the natural ingredients during 

 the heating to which tea is subjected in its manu- 

 facture. It has an exhilarating action, which mani- 

 fests itself by producing, among other effects, wake- 

 fulness and increased mental activity. Thein is 

 a nitrogenous proximate principle, having, when 

 pure, the form of shining, colourless, crystalline 

 needles. It is probably the most valuable con- 

 stituent of tea, for it has the remarkable power of 

 diminishing waste of tissue, and so economising 

 food. Hence it is that, with a limited quantity of 

 food, more work can be performed when tea is 

 taken, than without it ; and that, in old infirm 

 persons, where the desire for tea is so strong, the 

 waste and decay of the system are lessened. The 

 tannin of tea closely resembles the astringent 

 principle of oak-bark, gall-nuts, &c. ; and it is 

 doubtful if it confers any advantageous properties 

 to this beverage. In preparing tea for use, an 

 infusion should be made with boiling water ; but 

 the infusion should never be boiled, otherwise the 



