those which are solid yield to pressure a quantity of a liquid fatty oil. So that in reality all vegetable fats consist of two fatty substances, one of which is solid, and the other liquid, at ordinary temperatures.

Now, the same is the case with the animal fats-with those of beef and mutton for example, with the butter of milk, and with the oil contained in the yolk of the egg. All consist of a solid and a liquid fat, and in this fact we see a new analogy between our vegetable and our animal food.

But a still further and more intimate analogy exists between the solid portions of the fatty substances of the animal and vegetable kingdoms. When the solid fat of palmoil is properly purified it is found to consist of a solid, beautifully white, peculiar fatty body, to which the name of palmitine has been given. On the other hand, when beef and mutton fats are pressed from the oil they contain, and then purified, the most abundant substance obtained is a peculiar fat which is known by the name of stearine. remainder consists principally of palmitine.

The

Now, of these two fatty bodies the solid fat of all our domestic animals almost entirely consists. In beef and mutton fats the stearine is the more abundant. In human fat, in that of the goose, and in that of butter, the stearine and palmitine are in nearly equal proportions. It is the same. with vegetable fats. They consist of these two varieties in different proportions. In some the solid part consists chiefly. of stearine; in others, as in olive-oil, the stearine and palmitine are nearly equal in quantity; while in others again, as in palm-oil, the palmitine is the principal ingredient. Thus, as there is a kind of identity in nutritive quality and value among the compounds represented respectively by gluten in plants and by fibrin in animals, so there is an absolute identity of substance-as regards their solid part at least-among

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the fatty compounds which are met with in the eatable productions of both kingdoms.

The liquid portions of the fats of animals and vegetables, though generally regarded as being also for the most part identical, are not yet so well understood as their solid portions. It is a fact of practical interest, however, that they become rancid by exposure to the air sooner than the solid fats do. Hence hard butter keeps sweet longer than soft butter does. Hence, also, fat meat keeps longer, when salted, if the fat be hard. And hence the reason why, in finishing off fat animals for the butcher, especially if they are to be salted, it is usual to give dry food for some time before killing, that the fat may be hardened and the flesh made firm.

In another matter of detail I might show how, in still more minute matters, animal and vegetable kinds of food are nearly identical. When the parts of plants are burned in the open air they disappear for the most part, as I have already shown, and leave only a small proportion of ash be hind. This ash consists of a mixture of various substances, spoken of as their mineral, earthy, saline, or inorganic constituents.

The same takes place when the parts of animals are burned; and the mixture of mineral matters obtained consists, in either case, of the same substances, only differing more or less in their relative proportions. The same things occur in the ash of bread as are found in the ash of beef. In whatever degree, therefore, the nutritive properties of our food depend upon. the kind of mineral matter it contains, it is almost a matter of indifference whether we live upon an animal or a vegetable diet.

But to this interesting point I shall have occasion to return in a subsequent chapter.

*See THE PLANT WE REAB, p. 68.

CHAPTER VII.

THE BEVERAGES WE INFUSE.

THE TEAS.

Artificial drinks nearly all vegetable infusions, with or without subsequent chemical changes. Tea, extensive use of-The tea-plant; how its leaves are gathered.The aroma produced by the roasting.-Mode of preparing green and black tea from the same leaves.-Principal varieties of green and black tea-Differences in fragrance and flavour.-Ancient use of tea in China and the adjoining countries.-Introduction into Europe.-Total amount of tea produced.-Consumption in the United Kingdom.-Sensible effects of tea-Active chemical ingredients in tea.— The volatile oil, its action.-The theine, its composition.-Occurs in coffee, in maté, and in guarana.-Its effect in retarding the waste of the tissues.-Why tea is a favourite vith the poor.-The tannin, its properties and effects.-The gluten. -Tea-leaves and beans compared in nutritive quality.-Tartar mode of using tea. -Eating the exhausted leaves.-Tea varies in composition.-Proportion extracted by water varies.-How tea is coloured or dyed green in China.-Lie tea.-Maté or Paraguay tea.-Its ancient use in South America.-The Ilex paraguayensis or maté tree, where it grows, and how its leaves are collected.-Gongonha of Brazil, a variety of maté.-Frequent use of maté, and its effects.-Composition of the leaf. The volatile oil, the theine, the tannic acid, and the gluten.-Coffee-tea made from the leaf of the coffee tree.-Use of this tea in the Eastern Archipelago. -Effects observed from its use in Sumatra.-Contains the same active ingredients as the leaves of the tea trees.-Labrador tea used in North America.-Abyssinian tea or chaat.-Tasmanian teas.-Faham tea-Substitutes for Chinese tea and for maté.

THE two most important natural liquids, water and milk, have already been treated of; various artificial drinks, however, are prepared both in civilised and in semi-barbarous

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countries, and are in daily use among vast multitudes of men;-such as tea, coffee, and cocoa, beer, wine, and ardent spirits the preparation and effects of each of which are connected with interesting chemical considerations.

These drinks agree in being all prepared from or by means of substances of vegetable origin, and in being generally classed among the luxuries, rather than the necessarics of life.

The mode in which they are prepared, however, naturally divides these drinks into two classes. Tea, coffee, and cocoa are roasted and prepared before they are infused in water, and the infusion is then drunk without further chemical treatment. These are simple infused beverages. Beer, wine, and ardent spirits are prepared from infusions which, after being made, are subjected to important chemical operations. Among these operations is the process of fermentation, and hence they are properly distinguished as fermented liquors.

I shall consider these two classes of drinks, therefore, separately, and in the order in which I have mentioned them.

The infused beverages are drunk hot, fermented drinks are usually taken cold. The love of such warm drinks prevails almost universally. In frozen Labrador and snowy Russia, the climate might account for this predilection, but the craving is really deeper seated. The practice prevails equally in tropical and in arctic regions. In Central America the Indian of native blood, and the Creole of mixed European race, indulge alike in their ancient chocolate. In Southern America the tea of Paraguay is an almost universal beverage. The native North American tribes have their Ap allachian 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.

All Europe, too, has chosen its prevailing beverage. Spain and Italy delight in chocolate; France and Germany, and Sweden and Turkey, in coffee; Russia, Holland, and England in tea,-while poor Ireland makes its warm drink of the husks of the cocoa, the refuse of the chocolate mills of Italy and Spain.

All Asia feels the same want, and in different ways has long gratified it. Coffee, indigenous in Arabia or the adjoining countries, has followed the banner of the Prophet, wherever in Asia or Africa his false faith has triumphed. 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 all Russia, and is equally despotic in Moscow as in St. Petersburg. In Sumatra, the coffee-leaf yields the favourite tea of the dark-skinned population, while Central Africa boasts of the Abyssinian chaat as the indigenous warm drink of its Ethiopian peoples. Everywhere 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 poor human nature.

The beverages we infuse naturally arrange themselves into three classes. First, the teas or infusions of leaves. Second, the coffees or infusions of seeds. And third, the cocoas, which are more properly soups or gruels than simple infusions, as they are made by diffusing, through boiling water, the entire seeds of certain plants previously ground into a paste.

I. THE TEAS. Of teas there are many varieties in use in different parts of the world; but China tea, Paraguay tea or maté, and perhaps coffee-tea, are the most extensively consumed as national beverages. There are some others in constant though less general employment, to which it will be necessary somewhat briefly to advert.