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148 measure on its length. When very short the chyme contained in it affords no chyle, as may be observed in caterpillars; but when of great length, there is no doubt that the chyme is further elaborated, and chyle separated, just as it was in the chylific ventricle. It is scarcely possible that the small egg-shaped ventricle of the Lepidoptera could separate all the chyle necessary for the support of life, unless aided by the long intestine; neither could we see any necessity for the elongated and often convoluted shape of the latter, if its only use was to convey the unassimilating parts of the food to the rectum.

The progressive advance of the alimentary bolus, which we have thus traced through the canal, is caused by a distinct peristaltic motion, as strong, considering the relative size of the animals, as among the vertebrata. This alternate contraction and expansion is most observable in the crop and gizzard, which are supplied with the strongest fasciculi of muscles, and gradually becomes fainter towards the anal extremity.

In the higher animals, it is scarcely necessary to remind the reader, the chyle is absorbed from the alimentary canal by the lymphatic vessels, and conveyed to the venous blood, with which it repairs to the lungs or gills in order to be oxydised. No such conduits as absorbent vessels or veins existing in insects, the chyle merely transudes through the parietes of the digestive tube into the cavity of the body, whence it finds its way to a large cylindrical canal placed near the back, from which it receives an impulse which conveys it to different parts of the body.