THE ABSORPTIVE SYSTEM. 83 



process takes place. The bile is secreted from the 

 venous blood, and stored up in the gall-bladder, to 

 be used when needed in the digestion of food. The 

 blood, after being robbed of its bile and changed in 

 other respects not well understood, is again collected 

 and carried upward by the hepatic vein (20) and 

 emptied into the lower vena cava (16), which in turn 

 pours it into the heart, as shown here by the Aid. 

 This completes the portal circulation. 



Now let us go back to the same start- 



Route CCOnd * n Pi n ^ an d trace other portions of 



the digested food by another route; 



but which will ultimately lead to the same cavity of 



the heart. 



At this point we should observe how nicely every 

 organ of the body is adapted to perform its own 

 specific work. The blood-vessels spoken of under a 

 preceding head take up from the stomach and intes- 

 tines only certain portions of their contents, to do 

 which, they seem especially adapted. Other portions 

 are absorbed by the lacteals, which seem to be par- 

 ticularly suited for this purpose. 



Extending lengthwise through the cen- 



Te vim ln ter of eacn little villus > surrounded by 

 the meshes of the small veins just 

 described, is a single minute duct or rootlet called a 

 lacteal. Lac means milk, and it is owing to the 

 milk-like appearance of their contents that the term 

 lacteal is applied to these vessels. 



