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But what is the chemistry of all this new food and drink, unknown to that ancient life, the manners and features of which form so great a part of our study at school? What new craving in our common nature have they awakened, what old craving more agreeably satisfied ? What is their physiological action, in short, and upon what chemical constituents does it depend? Why have entire nations so readily fallen into the new habits, and why do they go pertinaciously cling to them?

By her fireside, in her humble cottage, the lonely widow sits; the kettle simmers over the ruddy embers, and the blackened teapot on the hot brick prepares her evening drink. Her crust of bread is scanty; yet as she sips the warm beverage — little sweetened, it may be, with the produce of the sugar cane, genial thoughts awaken in her mind; her cottage grows less dark and lonely, and comfort seems to enliven the ill-furnished cabin. When our suffering and wounded soldiers were brought down frozen and bleeding from the trenches before Sebastopol to the port of Balaklava, the most welcome relief to their sufferings was a pint of hot tea, which was happily provided for them. Whence this great solace to the weary and worn ? Why out of scanty earnings does the ill-fed and lone one cheerfully pay for the seemingly unnourishing weekly ounce of tea ? From what ever-open fountain does the daily comfort flow which the teacup gently brings to the careworn and the weak?

The answer we are enabled to give to these questions is still very imperfect. Recent chemical and chemico-physiological researches have indeed thrown much interesting light on the nature, composition, and mode of action of the warm infusions we delight to drink, and we can so far satisfactorily account for many of their effects. We may expect our present views, however, to be materially modified by the results of future research.

In the first place, past experiment has shown us that there is a remarkable chemical analogy among the four substances Chinese tea, Paraguay tea, coffee, and cocoa, which are chiefly employed for the preparation of infused beverages. All of them in the roasted state in which they are used, contain aromatic oils in minute proportion, to which the peculiar aroma of each is due. All contain also a proportion of an astringent substance resembling the tannin of gall-nuts or oak bark. In three of them, Chinese tea, Paraguay tea, and coffee, is found a variable quantity of a peculiar white crystalline body, to which the name of theine or caffeine has been given ; while in cocoa a different but similar body exists, which is known by the name of theobromine. Of these three constituents, which are all extracted by hot

water, two -- the volatile oil and the theine are known to exercise a peculiar action upon the system. The oil possesses narcotic properties, intoxicates, occasions headaches and giddiness, and sometimes paralysis in those who as tea-tasters are much exposed to its influence. New tea contains this oil in larger quantity than old tea does, and for this reason it is said that the Chinese rarely use their tea till it has been kept over a year. The small proportion of it which exists in tea as we get it in Europe, is not only harmless, but is probably one source of the soothing exhilaration which tea and coffee produce.

The theine, again, is a bitter substance possessing tonic or strengthening qualities, but distinguished particularly by the property of retarding the natural waste of the animal body. Most people are now aware that the chief necessity for food to a full grown animal, arises from the gradual and constant wearing away of the tissues and solid parts of its body. To repair and restore the worn and wasted parts, food must be constantly eaten and digested. And the faster the waste, the larger the quantity of food which must daily be consumed, to make up for the loss which this waste occasions. Now the introduction of a certain quantity of theine into the stomach lessens the amount of waste which in similar circumstances would otherwise naturally take place. It makes the ordinary food consumed along with it, go farther, therefore, -- or more correctly, lessens the quantity of food necessary to be eaten in a given time. A similar effect in a somewhat less degree, is produced by the volatile oil, and, therefore, the infusion of tea, in which both these ingredients of the leaf are contained, affects the rapidity of the natural waste in the tea-drinker in a very marked manner.

As age creeps on, the powers of digestion diminish with the failing of the general vigour, till the stomach is no longer able to digest and appropriate new food as fast as the body wears away.

When such is the case, to lessen the waste is to aid the digestive powers in maintaining the strength and bulk of the weakening frame. It is no longer wonderful therefore,' says our author, that tea and coffee should be favourites on the one hand . with the poor whose supplies of substantial food are scanty. * And on the other, with the aged and infirm, especially of the • feebler sex, whose powers of digestion and whose bodily substance • have together begun to fail. Nor is it surprising that the aged

female whose earnings are barely sufficient to buy what are • called the common necessaries of life, should yet spare a portion

of her small gains in procuring this grateful indulgence. She • can sustain her strength as well with less common food when

she takes her tea along with it; while she feels lighter at the same time in spirits, more cheerful, and fitter for the dull o work of life, because of this little indulgence.'

The wide prevalence of the taste for infused beverages illustrates in a marked manner the existence of common instinctive cravings among a large proportion of the human race. In tropical as well as arctic regions, the practice of using warm drinks equally prevails. Dr. Johnston follows the topography of these harmless stimulants in the following terms:

In Central America the Indian of native blood and the Creole of mixed European race indulge alike in their ancient chocolate. In South America the tea of Paraguay is an almost universal beverage. The native North American tribes have their Appalachian tea, their Oswego tea, their Labrador tea, and many others. From Florida to Georgia in the United States, and over all the West India islands, the naturalised European races sip their favourite coffee ; while over the northern States of the Union, and in the British Provinces, the tea of China is in constant and daily use.

• In Europe we have no means of knowing how long such tastes and practices have prevailed. The Romans, at their banquets, used cups and saucers made of silver richly embossed. They were nearly of the same shape as those now in use, and were employed for drinking hot water out of. Whether it was customary to infuse herbs in this water on any occasion we do not read. But in Holland and England sage tea was in use till a very late period ; and its antiquity is shown by the statement that the Dutch, in their early intercourse with China, carried out dried sage leaves as an article of traffic, and exchanged them against those of the Chinese tea-tree. Now, however, every country of Europe bas chosen for itself one or other of the familiar foreign beverages. Spain and Italy delight in cocoa ; France, Germany, Sweden, and Turkey in coffee ; Russia, Holland, and England in tea; while poor Ireland makes a warm drink for itself, out of the husks of the cocoa, the refuse of the chocolate mills of Italy and Spain.

• So all Asia feels the same want, and in different ways, has long gratified it. Coffee, indigenous in Abyssinia or the adjoining countries, has attached itself to the banner of the Arabian prophet, and has followed it wherever in Asia or Africa his false faith has tri. umphed. Tea, a native of China, has spread spontaneously over the hill country of the Himalayas, the table lands of Tartary and Thibet, and the plains of Siberia, has climbed the Altais, overspread Russia, and is equally despotic in Moscow as in St. Petersburg. In Sumatra the coffee-leaf yields the favourite tea of the darkskinned population, while Central Africa boasts of the Abyssinian chaat, as the indigenous warm drink of the Ethiopian people. Every where, unintoxicating and non-narcotic beverages are in general use -among tribes of every colour, beneath every sun, and in every condition of life. The custom, therefore, must meet some universal want of our common human nature.' (Vol. i. p. 56.)

This wide use of simply medicated drinks is remarkable enough. But it is still more remarkable that in so many different countries, and from so many different plants, different races of men— ignorant alike of chemistry and of physiology should have been led by a common instinct to select, for the purpose of preparing these drinks, vegetable substances which contain the same peculiar active ingredient. Thus the theine which characterises the Chinese leaf, is present not only in the coffee bean brought into use in Abyssinia and Arabia, in the coffee leaf employed as yet only in Sumatra, in the Maté or Paraguay tea which has been long collected among the forests of Paraguay, but also in the Guarana or Brazilian cocoa, in use among the natives of Brazil; while the true cocoa of Central America contains the very similar substance theobromine. This fact, which has been established beyond doubt by recent chemical research, is one of the most curious in the whole history of human instincts. Through how many successive trials, -after how wide and long an experience of bodily comfort and discomfort, - must half-civilised men in each of these countries have come to settle down into the general custom of using the several indigenous plants which modern times have found commonly employed among them. How very curious that the chemistry of our day should discover that in so many cases the plants thus selected should be capable of yielding to water the same chemical and physiological ingredient!

The passion for fermented drinks is akin to the love of infused beverages, but it stands upon a somewhat different ground. It is not instinctive in the same sense as the desire for warm infusions. It has not everywhere led the different races of men through long trial and research to the means of gratifying it. These means have rather sprung up of themselves before mankind in certain parts of the world, and have thus awakened the passion which, if it existed in human nature at all, would otherwise have remained dormant.

Thus, in tropical climates, where palm trees flourish, an accidental wound to the topmost shoot causes a copious flow of sweet sap, which, of its own accord, speedily ferments and produces an agreeable intoxicating drink. How early in eastern climes must this grateful liquor have become familiar to the primeval races? How natural it was in them to make use of it!

So also in Mexico the American aloe pours its copious juice into its own central cup, and there in a brief space produces the Mexican pulque, so pleasing to the native palate. And where the grape vine bears its luscious bunches the expressed juice soon begins to move and sparkle with bubbles of living

And a yet

gas, and the crude heavy liquor changes spontaneously into the cheerful and exhilarating wide. Indeed the juices of nearly all fruits, even of our more northern ones—the apple, the pear, the plum, the gooseberry, and a hundred others—naturally produce their own peculiar varieties of intoxicating drink. Fermented liquors, therefore, are natural beverages, which 'man could not avoid becoming acquainted with, and of which in many countries it required little ingenuity to obtain a continued and abundant supply. It was probably some fortunate accident which led to the discovery of the mode of preparing sweet liquids from sprouted grain (malt), and of converting them into an exhilarating drink by mixing them with other liquids already in fermentation. A rarer accident, no doubt, led to the singular custom of chewing grains and roots, still practised in Peru, for the preparation of fermented chica, and in the South Sea Islands for the manufacture of the favourite ava. rarer accident, at a more modern period, taught some sleepless Arabian alchemist, — torturing substance after substance in his crucibles and alembics,- how to extract the fierce spirit from these agreeable drinks, and brought up, as it were, from the bottom of Pandora's box, that Alcohol which has since inflicted so many evils upon the world.

In the chemical history of these fermented drinks there are many things which will well repay the careful student who is desirous of thoroughly understanding this important chapter of the 'chemistry of common life.' In all cases, for example, and whatever may be the source of the liquid we employ, the same chemical substance undergoes the same chemical change during the process of fermentation. In every instance we start with grape sugar—that is, the kind of sugar which exists ready formed in the grape and other fruits. If we wish to employ grain we make it sprout, and thus produce within it a peculiar substance called diastase, which, when the grain is crushed and steeped in warm water, converts the starch of the grain into grape sugar, and dissolves it, forming the sweet wort. To this solution of grape sugar we add a ferment, usually yeast, if it does not naturally contain one, as grape and palm tree juices do. Through the action of the ferment the grape sugar is changed, always in the same chemical way, so that sparkling carbonic acid gas and intoxicating alcohol are in every case produced. At the same time a peculiar ethereal oil, in small proportion, is formed. This is different in the juice or sap of each different fruit or tree, and hence each variety of fermented drink derives its own peculiar bouquet.

Then how singular and worthy of study are the effects they

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