J48 ANATOMY AND PHYSIOLOGY 



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 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 ~}se 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, 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 oi 

 muscles, and gradually becomes fainter towards tb 

 anal extremity. 



In the higher animals, it is scarcely necessary i 

 remind the reader, the chyle is absorbed from th 

 alimentary canal by the lymphatic vessels, and con 

 veyed to the venous blood, with which it repairs 

 the lungs or gills in order to be oxydised. No sue 

 conduits as absorbent vessels or veins existing in ii 

 sects, the chyle merely transudes through the pariete 

 of the digestive tube into the cavity of the bod} 

 whence it finds its way to a large cylindrical cana 

 placed near the back, from which it receives an im 

 ?ulse which conveys it to different parts of the body 



