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ANATOMY AND PHYSIOLOGY 
measure on its length. When very short the chyme 
contained in it affords no chyle, as may he observed 
in caterpillars; hut when of great length, there is 
no doubt that the chyme is further elaborated, and 
chyle separated, just as it was in the chylific ven- 
tricle. 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 
un assimilating 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, con- 
sidering the relative size of the animals, as among 
the vertebrata. This alternate contraction and ex- 
pansion 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 con- 
veyed 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 in- 
sects, 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 im- 
pulse which conveys it to different parts of the body. 
