That it would soon become a most valuable article of diet amongst the laboring classes, and on ship board particularly, if, once brought into use, there can be no doubt. The coffee-tree can be grown to advantage for the leaf in the lowlands of every tropical country, where the soil is sufficiently fertile, whilst it requires a different soil and climate to produce the fruit[7]. Dr. Hooker, in the Jury Reports, observes upon the prepared coffee leaves, submitted by Dr. Gardner, of Ceylon, to be used as tea leaves, that they are worthy of notice as affording a really palatable drink when infused as tea is; more so, perhaps, than coffee is to the uninitiated. That this preparation contains a considerable amount of the nutritious principles of coffee, is evident from the analysis; but as the leaves can only be collected in a good state at the expense of the coffee bush, it is doubtful whether the coffee produced by the berries be not, after all, the cheapest, as it certainly is the best.
TEA.
The immense traffic in the produce of this simple shrub, the growth of a remarkable country, hitherto almost entirely isolated from the western nations, is one of the most remarkable illustrations of the enterprise and energy of modern commerce. The trade in tea now gives employment to upwards of 60,000 tons of British shipping, and about ten millions sterling of English capital, producing a revenue to this country of nearly six millions sterling.
Every reflecting man will admit that articles of such vast consumption as tea and coffee (amounting together to more than 343,500 tons annually), forming the chief liquid food of whole nations, must exercise a great influence upon the health of the people.
There is scarcely any country in the world in which a dietetic drink or beverage resembling tea, is not prepared, and in general use, from some exotic or indigenous shrub. The two chief plants laid under contribution are, however, the Chinese tea-plant, and a species of holly peculiar to South America, producing the Paraguay tea. Astoria theiformis is used at Santa Fe as tea. The leaves of Canothus Americanus, an astringent herb, have been used as a substitute, under the name of New Jersey tea.
It has been a matter of surprise why tea should be so much sought after by the poorer classes, since by many it is looked on more as a luxury than of use to the human system. The manner in which it acts, and the cause why it is so much in demand by all classes, is satisfactorily explained by Liebig; and the benefit, therefore, which will be conferred by selling it at a low rate, and thus placing it within the means of all, has at last come to be duly appreciated. Liebig says, without entering minutely into the medical action of caffeine, theine, &c., it will surely appear a most striking fact, even if we were to deny its influence on the process of secretion, that the substance, with the addition of oxygen and the elements of water, can yield taurine, the nitrogenised compound peculiar to bile:—
| Carbon. | Nitrogen. | Hydrogen. | Oxygen. | ||
| 1 atom caffeine or theine | = | 8 | 2 | 5 | 2 |
| 9 atoms water | = | .. | .. | 9 | 9 |
| 9 atoms oxygen | = | .. | .. | .. | 9 |
| = 2 atoms taurine | 8 | 2 | 14 | 20 | |
| = | 2 | 4 | 9 | 10 |
To see how the action of caffeine, theobromine, theine, &c., may be explained, we must call to mind that the chief constituent of the bile contains only 3.8 per cent. of nitrogen, of which only the half, or 1.9 per cent., belongs to the taurine; bile contains, in its natural state, water and solid matter, in the proportion of ninety parts by weight of the former, to ten of the latter. If we suppose these ten parts, by weight of solid matter, to be chloric acid, with 3.87 per cent. of nitrogen, then 100 parts of theine would contain 0.171 of nitrogen in the shape of taurine. Now this quantity is contained in 0.6 parts of theine, or 2 grains 8/10ths of theine can give to an ounce of bile the nitrogen it contains in the form of taurine.
Although an infusion of tea contains no more than the one-tenth of a grain of theine, still, if it contribute in point of fact to the formation of bile, the action even of such a quantity cannot be looked upon as a nullity. Neither can it be denied, that in the case of an excess of non-azotised food, and a deficiency of motion, which is required to cause the change of matter of the tissues, and thus to yield the nitrogenised product which enters into the composition of the bile, that in such a condition the health may be benefited by the use of compounds which are capable of supplying the place of the nitrogenised substances produced in the healthy state of the body, and essential to the production of an important element of inspiration. In a chronical sense, and it is this alone which the preceding remarks are intended to show, caffeine, or theine, &c., are, in virtue of their composition, better adapted to this purpose than all nitrogenised vegetable principles. The action of these substances in ordinary circumstances is not obvious, but it unquestionably exists. Tea and coffee were originally met with among nations whose diet was chiefly vegetable.
Considerable discussion has taken place regarding the tea plants; some say that there is only one species; others that there are two or three. Mr. Fortune, who visited the tea districts of Canton, Fokien, and Chekiang, asserts that the black and green teas of the northern districts of China are obtained from the same species or variety, known under the name of Thea Bohea. Some make the Assam tea a different species, and thus recognise three: T. Cantoniensis or Bohea, T. Viridis, and T. Assamica. The quality of the tea depends much on the season when the leaves are picked, the mode in which it is prepared, as well as the district in which it grows. The green teas include Twankay, Young Hyson, Hyson, Gunpowder, and Imperial; while the black comprise Bohea, Congou, Souchong, Oolong, and Pekoe. The teas of certain districts, such as Anhoi, have peculiar characters.