. Animal and vegetable physiology, considered with reference to natural theology. Biology; Physiology; Plant physiology; Natural theology. NUTRITION IN THE ASTERIAS. 77 stomach; and the stomach continued into a regular intestine, which takes two turns in the cavity of the body, before it terminates. The alimentary tube in the lower animals frequently ex- hibits dilatations in different parts: these, if situated in the beginning of the canal, may be considered as a succession of stomachs; while those that occur in the advanced por- tions are more properly denominated the great intestine, by way
. Animal and vegetable physiology, considered with reference to natural theology. Biology; Physiology; Plant physiology; Natural theology. NUTRITION IN THE ASTERIAS. 77 stomach; and the stomach continued into a regular intestine, which takes two turns in the cavity of the body, before it terminates. The alimentary tube in the lower animals frequently ex- hibits dilatations in different parts: these, if situated in the beginning of the canal, may be considered as a succession of stomachs; while those that occur in the advanced por- tions are more properly denominated the great intestine, by way of distinction from the middle portions of the tube, which are generally narrower, and are termed the smalt in- testine. We often see blind pouches, or cseca, projecting from different parts of the canal; this is the case with the intestine of the Jiphrodita aculeata, or sea-mouse. The in- testine being generally longer than the body, is obliged to be folded many times within the cavity it occupies, and to take a winding course. In some cases, on the other hand, the alimentary tube passes in nearly a straight line through the body, with scarcely any variation in its diameter; this is the case with the Ascaris, which is a long cylindric worm; and nearly so with the Lumbricus terrestris, or earth-worm. In the Nais, on the contrary, as shown in Fig. 259, the alimentary tube presents a series of dilatations, which, from the transparency of the skin, may be easily seen in the living animal. The food taken in by these worms is observed to be transferred from the one to the other of its stomachs, backwards and forwards many times, before its digestion is accomplished. The stomach of the Leech is very peculiar in its struc- ture: its form, when dissected off, and removed from the body, is shown in Fig. 2G0. It is of great capacity, occu- pying the larger part of the interior of the body; and its ca- vity is expanded by folds of its internal membrane into se- veral pouches (c
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