Part 2 (1/2)

4. My leg has two parts:

my thigh, and my lower leg;

and three joints:

my hip joint, my knee joint, my ankle joint.

5. My foot is used in standing, walking, running, skating, and jumping:

my instep, my toes, the sole of my foot, the ball, the hollow, the heel, my toe joints, and my toe nails, which protect my toes.

QUESTIONS FOR THE FORMULA.

1. Which are your limbs?

2. Tell about your arm.

3. Tell about your hand.

4. Tell about your leg.

5. Tell about your foot.

[Ill.u.s.tration: THE ELBOW JOINT.

(A hinge joint.)]

[Ill.u.s.tration: THE HIP JOINT.

(A ball-and-socket joint.)]

Some joints, as those of the skull, are immovable; some, as those of the spine, may be moved a little; and others more or less freely, as those of the limbs. In machines, the parts which move upon each other need to be oiled, to keep them from wearing out; but the joints of our bodies oil themselves with a thin fluid, called _synovia_. This fluid resembles the white of an egg, and comes from a smooth lining inside of the joints. The ends of the bones which form joints are covered by gristle or _cartilage_, and are fastened together by very strong, silvery white bands, called _ligaments_. A sprain is caused by overstretching or tearing some of these ligaments.

QUESTIONS ON THE LIMBS AND JOINTS OF THE BODY.

What is the trunk of your body?--”All the body but the head and limbs.”

Which are your limbs?--”My two arms and my two legs.”

How many limbs have you?--”Four.”

How many parts has your arm?--”Two parts: my upper arm and my fore-arm.”

How many parts has your leg?--”Two parts: my thigh and my lower leg.”

How many joints has your arm?--”Three joints: my shoulder joint, my elbow joint, my wrist joint.”

How many joints has your leg?--”Three joints: my hip joint, my knee joint, my ankle joint.”