The greatest protection against such an emergency is to train a child to understand the construction of her own body and to impress upon her, in early days, her obligations to the invisible Friend and Guardian of her life, the "Former of her body and the Father of her spirit," who has committed to her care so precious and beautiful a casket. And the more she can be made to realize the skill and beauty of construction shown in her earthly frame, the more will she feel the obligation to protect it from injury and abuse.
It is a singular fact that the war of fashion has attacked most fatally what seems to be the strongest foundation, and defense of the body, the bones. For this reason, the construction and functions of this part of the body will now receive attention.
The bones are composed of two substances, one animal, and the other mineral. The animal part is a very fine network, called cellular membrane. In this are deposited the harder mineral substances, which are composed principally of carbonate and phosphate of lime. In very early life, the bones consist chiefly of the animal part, and are then soft and pliant. As the child advances in age, the bones grow harder, by the gradual deposition of the phosphate of lime, which is supplied by the food, and carried to the bones by the blood. In old age, the hardest material preponderates; malting the bones more brittle than in earlier life.
The bones are covered with a thin skin or membrane, filled with small blood-vessels which convey nourishment to them,
Where the hones unite with others to form joints, they are covered with cartilage, which is a smooth, white, elastic substance. This enables the joints to move smoothly, while its elasticity prevents injuries from sudden jars.
The joints are bound together by strong, elastic bands called ligaments, which hold them firmly and prevent dislocation.
Between the ends of the bones that unite to form joints are small sacks or bags, that contain a soft lubricating fluid. This answers the same purpose fur the joints as oil in making machinery work smoothly, while the supply is constant and always in exact proportion to the demand.
If you will examine the leg of some fowl, you can see the cartilage that covers the ends of the bones at the joints, and the strong white ligaments that bind the joints together.
The health, of the bones depends on the proper nourishment and exercise of the body as much as that of any other part. When a child is feeble and unhealthy, or when it grows up without exercise, the bones do not become firm and hard as they are when the body is healthfully developed by exercise. The size as well as the strength of the bones, to a certain extent, also depend upon exercise and good health.
[Illustration: Fig. 61]