326 PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



by the great length of the intestines, still more by the 

 many folds of the mucous membrane (valvules conniventes) 

 (Fig. 207), but most of all by the villi. These micro- 

 scopic hairlike projections 



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Fig. 208. — Two of the villi, greatly 

 enlarged ; one showing blood cap- 

 illaries, the other, the lacteals : 

 ep, epithelium. 



cover the surface as thick- 

 ly as the pile of velvet or 

 the tufts of Brussels car- 

 pet. They give a velvety- 

 feel to the mucous mem- 

 brane (Fig. 208). Each 

 villus contains two kinds 

 of absorbent vessels — viz., 

 capillary blood vessels and 

 lacteals. These, though 

 separated in the figure, 

 are both of them in each 

 villus. 

 Two Modes of Absorption. — The food is ab- 

 sorbed in two ways — viz., by blood capillaries and by lac- 

 teals. The blood capillaries contain a circulating current, 

 and therefore take up the food and carry it along with 

 the blood. The lacteals, on the contrary, are purely 

 absorbent, and they end in blind, fingerlike extremities, 

 and therefore suck up the liquid food. Whatever of food 

 is absorbed by the stomach is wholly by blood capil- 

 laries. But the intestines are specially organized for 

 absorption in both ways. The food is divided between 

 these two modes. The sugars are absorbed mainly by 

 the capillaries, the fats by the lacteals, while the pep- 

 tones are divided between them. 



Course of Each to the General Circulation. — 

 That taken up by the capillaries is carried to the por- 

 tal vein ; thence it passes through the liver, and by the 

 hepatic vein it reaches the vena cava ascendens and by 

 it is carried to the heart, and is thence distributed every- 



