=Volatile Oil=—Is the principle which imparts to tea its peculiar flavor and aroma, and upon the amount contained in the dried leaves depends the strength and pungency of the infusion. It is present only in very small quantities, but is, nevertheless, very potent in its effects, the proportions ranging, according to Mulder, from 0.6 per cent. in Black tea to 0.80 in Green, but averaging 0.75 in all good teas. It is found by distilling the tea with water, is lighter in body than water, citron-yellow in color, resinifying on exposure, solidifying with cold, and exerting a powerfully exciting or stimulating effect on the system. But there being no chemical analysis of this constituent extant, its exact effect on the human system is difficult to define. By some authorities it is claimed to produce wakefulness, acting, it is said, in the same manner as _digitalis_ (fox-glove) which, when taken in overdoses, causes anxiety and inability to sleep. It is a well-known fact that Green teas produce these effects, while Black does not, the excessive fermentation to which the latter are subjected in the process of curing, dissipating the volatile oil to a greater extent, or, more properly, altering its general character not only in effect but also in flavor. =Gum or Gluten=—If it is necessary to estimate the quantity of gum or gluten in tea, as sometimes happens, evaporate an aqueous decoction of the leaves to an extract, and treat the residue with methylated spirit, filter and wash off with hot water, after which evaporate the solution to dryness, next weighing and burning it to an ash and deduct the mineral residue from the original weight of the leaves. Tea extract also yields a large quantity of ammonia when boiled with potash, and it is probable that this character may prove valuable also in testing the genuineness of tea. Tea leaves under an extraordinary amount of ammonia, when submitted to this test, are found to be remarkably rich in nitrogen, the determination of which is also a means of identification. It may also be here remarked that when tea-leaves have been exhausted by infusion, alcohol is still capable of extracting a considerable amount of soluble matter. This alcohol extract, when infused in boiling water, furnishes a liquor which smells and tastes strongly of tea, which, were it not for the expense of the solvent and trouble attending its separation, could no doubt be profitably employed. A fixed oil composed of equal parts of oleine and stearine, serving many purposes, medicinal, illuminating and others, is extracted from the seeds of the tea-plant in many parts of China and Tartary. The other substances extracted from the tea-leaf consists principally of those which, in various proportions, enter into the composition of all plants and include a modification of constituents analagous to sugar, fat, salts, starch and water. The fibre, tannin, legumen coloring matter and a certain quantity of ash