274 



THE COMPLETE GRAZIER. 



BOOK II. 



which is brought to them in the intestinal arteries ; notably it has gained 

 soluble nitrogenous compounds and soluble carbohydrates. All the blood 

 collected from the intestinal walls is poured ultimately into a large vessel 

 called the portal vein, which enters the liver and distributes its contents 

 among the capillaries of that organ, so that the blood from the intestine 

 is submitted to the action of the liver, though what that action is it 

 is not necessary here to inquire. The blood of the liver is in the end 



Fig. 66. Vertical Sectioivof the Mucous Membrane of the Small Intestine 

 (Magnified 150 diameters). 



Two villi are represented. In the one on the right hand the dilated lacteal alone is 

 shown, in the other the blood capillaries and lacteal are both seen injected, the lacteal 

 white, the blood-vessels dark ; the section is carried through the tubular glands into the 

 sub-mucous tissue ; a, the lacteal vessels of the villi ; a', the horizontal lacteal, which they 

 join ; b, capillary blood-vessels in one of the villi ; c, small artery, conveying blood to the 

 capillaries of the villus ; d, vein, carrying blood away ; c, the 'epithelium cells covering the 

 villi ; g, tubular glands (called crypts of Lieberkiihn), which secrete the succus entericus, 

 or intestinal juice ; i, the sub-mucous layer. A, cross-section of three tubular glands more 

 highly magnified. 



collected by the hepatic veins, which pour their contents into a great 

 vein called the posterior vena cava, and this passes forward and opens 

 directly into the right side of the heart. 



Let us return to the intestine and find out what becomes of the fats 

 of the food. Very minute quantities of fatty matter may find their way 

 into the blood capillaries of the villus, and so pass into the portal vein, 

 but by far the greater quantity of the particles of emulsified fat pass 

 into the villus and enter, not the blood capillaries, but the lacteal. It 

 will presently be useful to inquire exactly how this is effected, but it 

 is more to the point now to see what becomes of the fat after it enters 

 the lacteal. The lymphatics of the small intestine resemble the blood 

 capillaries in that they coalesce into larger tubes or vessels, and it is 

 because, after a meal rich in fatty matters, the lymphatics of the small 



