We have stated that starch and gum can be turned into sugar by art,—­but as no chemist has yet succeeded in imitating an animal substance, the change of these three into fat takes place only in the body.  There are proofs enough within general observation, that one object of this portion of our diet is the supply of fat.  The Esquimaux fattens on his diet of blubber and train-oil; the slaves on the sugar-plantations grow fat in the boiling-season, when they live heartily on sugar; the Chinese grow fat on an exclusively rice diet,—­and rice is chiefly starch.  But one of the most interesting observations of the transformation of sugar into a fat is that made by Huber upon bees.  It was the discovery, that bees make their wax out of honey, and not of pollen, as was formerly believed.  When Huber shut up some bees in a close hive, and kept them supplied with pure honey or with sugar alone, they subsisted upon it, and soon began to build the comb.  Wax is a fat, and the honey which is eaten by the bee is partly transformed into wax in his body.  In about twenty-four hours after his stomach has been filled with honey, thin plates of wax appear on the scales of his abdomen, having oozed through eight little openings in the scales and there hardened.  Of this they build their cells.

We have wandered far from the consideration of the propensity of certain species of plants to take up special compound substances from the earth; but the wide-spread silex, with which we set out, displayed so interesting a field of observation, that it could not be resisted, and encouraged a disposition to rove, which has been to us instructive and entertaining.  To return to plants,—­we find they make use of compounds for certain special ends; but, as we have seen, the whole vegetable kingdom uses the eight or ten primitive elements which it has in common with the animals, and out of these alone forms the infinite variety of products which we derive from it for food and various economical and aesthetical purposes.  Among the many processes of Nature whose contemplation fills us with ever new delight, this power of the adaptation of a few means to an infinite number of ends is one of the most enchanting.  We endeavor to explain by chemical laws the reduction of the materials which earth and air furnish, to a form in which they can be appropriated by the tree; by endosmose and exosmose we think we have overcome the obstacles to a clear comprehension of the circulation of the sap; and by a cell-theory we believe we have explained the whole growth of wood and leaves and fruit.  But what microscope or what alembic shall ever tell us why a collection of tubes and cells in one tree creates the most wholesome and delicious fruit, while in another an organization precisely similar, so far as we can discern, produces only harsh and poisonous berries? why the acacia tribe elaborate their gum, the pine family turpentine, the almond prussic acid, the sorrels oxalic acid? why the tall calisaya-tree of the Andes deposits in its bark the valuable medicine cinchona, and the oak, the hemlock, the tea-plant, and many others, make use of similar repositories to lay up stores of tannic acid?  The numberless combinations of the same materials, and the wonderful power which rests in a single seed to bring about with unvarying uniformity its own distinct result, attest to us every day the admirable wisdom and goodness of the Creator.