DIGESTION. 221 



discuss, in detail, the process of digestion, as it takes place in. each stage 

 of the journey of food through the alimentary canal. 



FIG. 164. Diagram of the Alimentary Canal. The small intestine of man is from about 3 to 4 

 times as long as the large intestine. 



The Teeth. 



During the course of his life, man in common with other mammals, 

 is provided with two sets of teeth, the first set is called the temporary or 

 milk teeth, which makes its appearance in infancy, and is in the course of 

 a few years shed and replaced hy the second or permanent set. 



The temporary or milk teeth have only a very limited term of 

 existence. 



They are ten in number in each jaw, namely, on either side from the 

 middle line two incisors, one canine, and two deciduous molars, and are 

 replaced by ten permanent teeth. 



The number of permanent teeth in each jaw is, however, increased to 

 sixteen, by the development of three others on each side of the law. 



