112 THE HUMAN BODY. 



kind of vessels called lacteals, which will be described 

 presently, whose special work it is to take up fat. 



6, As the muscular walls of the intestine contract and 

 relax, these little villi are worked in the mass of food; 

 and they draw in the digested part as the fine rootlets of 

 a plant draw up liquid nourishment from the earth in 

 which they stand. 



7, As the chyme and chyle pass on down the small 

 intestine, the digestible portion is constantly growing 

 less, until at length it has all been taken up, the chyle 

 chiefly by the lacteals, and the other portions of the 

 food chiefly by the blood-vessels; and what remains is 

 indigestible and useless. 



8, The food, having thus become a part of the blood, is 

 carried through the body, and permitted to soak out 

 through the walls of the capillary vessels, to feed each 

 particle of living substance. 



9, Water, and mineral matters like salt, that are dis- 

 solved in water, need no digestion, and are taken up by 

 the vessels in all parts of the canal. 



SECTION III. The lymphatic system. 1, This is a 

 system of tubes and glands, the tubes resembling the 

 blood-vessels in some respects. They begin with hair-like 

 tubes running among the capillaries, and much like them. 

 These unite to form larger tubes, which unite with others, 

 and so on, until they have all been united into two tubes, 

 each about as large as a slate-pencil. These open into the 

 large veins, not far from the heart. They are called the 

 thoracic duct and the right lymphatic duct. 



2, But the lymphatic system is not just like the system 

 of blood-vessels. The lymph, as the fluid which they con- 



