248 



THE SKELETON 



Still another form of union is seen in the joining of the 

 ribs to the sternum. Here a band of cartilage connects 

 the two bones, and the flexibility of the cartilage permits 

 of some motion. 



CLASSIFICATION OF JOINTS. 



Hygiene of the skeleton. — The formation of bone is 

 directly dependent upon the amount of lime salts in 

 the blood supply. On this account it is essential that 

 children, whose percentage of bone stiffening matter is 

 naturally small, should have a diet rich in these mineral 

 salts. Milk is especially rich in such material, and on this 

 account, as well as for its generally nutritious composition, 

 furnishes an ideal food. The disease known as rickets is 

 a result of such lack of bone-making material in the blood. 



Bones do not increase in length and size uniformly, the 



