224 DIGESTION. 



whilst it was going on, opens and permits the 

 chyme to pass into the small intestines. Here it 

 is made still more fluid, by the addition of various 

 juices, and becomes of a milky whiteness, and now 

 it is called chyle. In this state it meets with the 

 bile, which is supposed to have the property of 

 separating the nutritious from the useless parts. 



The reader has learnt that the inner surface of 

 the small intestines is lined by villi, which are 

 the mouths of lacteals. These are now actively 

 at work, taking up the milky part of the chyle, 

 and carrying it to a number of glands, where it 

 undergoes some farther change. 



From these it is carried forwards, till all the 

 lacteals are at last collected into one large duct, 

 which conveys the stream of chyle, now fitted for 

 mixing with the blood, along the spine, up as high 

 as the neck ; here it opens into one of the great 

 veins, and after passing through the heart and 

 lungs, becomes perfectly mixed, and ready for 

 nutrition. 



These are the changes undergone by our food 

 before it becomes blood, and they come under the 

 general term, digestion. 



Questions. 



What is there concealed in the gums of infants ? 



Is each tooth separate, and in what is it enclosed ? 



Why have very young children no teeth ? 



In what order do the teeth appear 1 



What is the first set called, and how long does i 



