But if the proof of this must be admitted to be still imperfect with regard to the lowest tribes of animals, it is certain that, as we ascend in the scale of organization, the nutritive apparatus is uniformly arranged in this mode. Every animal of every class large enough to be distinctly visible, and the structure of which is not rendered inappreciable by the transparency of its solids and fluids, is manifestly provided with a distinct internal reservoir for containing its food. On the internal surface of this reservoir open the mouths of vessels, minute in size but countless in number, which absorb the food from the stomach. Fig. XI. shows these vessels opening on the inner surface of the stomach, the white points representing their mouths, turgid with the food they have absorbed. Fig. XII. exhibits magnified views of the same vessels, the points representing their open mouths, and the lines the vessels themselves in continuation with their mouths. Fig. XIII. shows the appearance of the inner surface of the intestine soon after the animal has taken food; the smaller white lines (1 1 1 1) representing the absorbent vessels full of digested food, and the larger lines (2 2 2 2) the trunks of the absorbent vessels formed by the union of many of the smaller. [Illustration: Fig. XI.] [Illustration: Fig. XII.] From this account, it is clear that the absorbing vessels of the stomach perform an office precisely analogous to that of the spongeoles of the root. What the soil is to the plant, the stomach is to the animal. The absorbing vessels diffused through the stomach, as long as the stomach contains food, are in exactly the same condition as the spongeoles of the root spread out in the soil; and the absorbing vessels of the stomach are as much and as constantly in contact with the aliment, which it is their office to take into the system, as the spongeoles of the root. Such, then, is the expedient adopted to render the function of nutrition compatible with the function of locomotion. A reservoir of food is placed in the interior of the animal, provided with absorbent vessels which are always in contact with the aliment. In this mode, contact with aliment is not disturbed by continual change of place; the organic process is not interrupted by the exercise of the animal function. [Illustration: Fig. XIII.]