Lettson furnishes a calculation, partly his own and partly from other sources, in which he endeavors to prove how much is, in his view, unnecessarily expended by the poor for tea. But the observations of Liebig, if correct, and in all probability they are, offer a satisfactory explanation of the cause of the partiality of the poorer classes, not alone for tea, but for tea of an expensive and therefore superior quality. “We shall never certainly,” he says, “be able to discover how people were led to the use of hot infusions of the leaves of a certain shrub (tea) or a decoction of certain roasted seeds (coffee); some cause there must be which would explain how the practice has become a necessary of life to whole nations.” But it is still more remarkable 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 natural families, the product of different quarters of the globe, could hardly have presented itself to the boldest imagination, recent research having shown in such a manner as to exclude all doubt that the _caffeine_ of coffee and the _theine_ of tea are in all respects identical. And without entering into the medical action of this principle, it will surely appear a most startling fact, even if we deny its influence on the process of secretion, that this substance, with the addition of oxygen and the elements of water, can yield _taurine_, the nitrogenous compound peculiar to bile. So that if an infusion of tea contain no more than 1-10 of a grain of theine, and contributes, as has been shown, to the formation of bile, the action, even of a such a small quantity, cannot be looked upon as a nullity. Neither can it be deemed that in the case of non-atomized food or a deficiency of the exercise required to cause a change of matter in the tissues, and thus to yield the nitrogenized product which enters into the composition of bile, the health may be benefited by the use of compounds essential to the production of this important element of respiration. In a chemical sense, and it is this sense alone that theine is in virtue of its composition better adapted to this purpose than all other nitrogenized vegetable principles yet discovered. To better prove how the action of tea may be explained, we must call to mind that the chief constituents of the bile contain only 3.8 per cent. of nitrogen, of which only one-half belongs to the _taurine_. Bile contains in its natural state water and solid matter in the proportion of 90 parts of the former to 10 parts of the latter, and if, we suppose, these 10 parts of solid matter to be cholenic acid with 5.87 per cent. of nitrogen, then 100 parts of bile must contain 0.171 of nitrogen in the form of taurine, which quantity is contained in .06 parts of theine, or, in other words, 272 grains of theine can give to an ounce of bile the quantity of nitrogen it contains in the form of taurine. The action of