exposed, and remains in a defenceless state; but by instinct—which I shall explain hereafter-he hides himself away in some retired spot, where he can wait in security till a new shell is formed. This is done by a hard substance resembling lime, which is left on the outward surface of the skin by the blood in its circulation, that grows firm and hard, and finally fits over the body and makes a new shell or covering.

51. Insects have no internal skeleton, but are provided with a hard external covering, which serves to support their motions, and protect their organs. In some it forms a complete shell. In others it consists of a tough muscular coat divided into rings. Clams and oysters have no bones. They are supplied with muscles, which permit them to move, and living in a warm house, they can spend their life answering the end for which they were created.

52. Fishes are covered with a thick, strong skin, and generally have scales arranged over each other, like the shingles of a house. Their bodies are covered with a thin slimy matter, which defends them from the water, and they breathe by means of their gills, through which they take in air.

53. Crocodiles are covered with a thick coat of scales, which are proof against a bullet, or blows of any kind. This covering appears very fine, resembling carved work. The crocodile is from twenty to thirty feet in length, and can run with the speed of a man,

50. How is the new shell formed? 51. Describe the bones of insects? What is their use in different animals? What have clams and oysters instead of bones? How are they enabled to move? 52. Describe the covering of fishes? How do they breathe? 53. Describe the covering of crocodiles. How great is their speed?

BONES OF THE TURTLE.

47

and being insensible to blows, is very dangerous. When a person is pursued by one, he can scarcely avoid him in any other way than by making a turn; for they are so long that it is difficult for them to turn their bodies around.

54. The turtle and tortoise have an upper and lower shell, joined at the sides, through which the head, tail, and four extremities extend. The upper shell is formed by the extension and enlargement of the ribs and part of the back-bone, and the lower one by the sternum or breast-bone, so that a part of their skeleton is on the outside of their bodies; the ribs, breast-bone, and vertebræ, forming their shell or covering. Their stomach is simple, their intestines long, and they are capable of going without food for a long time.

55. They are very tenacious of life, have strong muscles, especially in the mouth and throat; for, when they bite anything, they will not open their teeth, even if whipped or beaten with a stick. A turtle once caught a fine little gosling in the water by the wing, and held him fast by the teeth, and would not let him go till some one shot him with a rifle, which stunned him. A person once caught a turtle, cut off his head, and threw it away; but for several days afterward, the body moved around the house as though alive, owing probably to muscular contraction. I might tell a great many interesting facts about different birds and animals, but I must pass on to different subjects.

The bones are covered by a thin substance called

53. How can crocodiles be avoided? 54. Describe the covering of the turtle and tortoise. How is the upper shell formed? How is the lower shell formed? Do they require much food? 55. How strong are their muscles in the mouth and throat? What anecdote is related of a turtle?

periosteum. When this is diseased people have the

rheumatism.

56. Perhaps some will say, why do not the joints rub together and prevent their moving? This would be the case if they were not continually moistened by a fluid called synovia, which enables them to move very easily, in the same way that wheels can turn much faster and better when well oiled. If there were nothing to moisten our bones, they would creak, and make as much noise as some carriage-wheels do when not properly oiled.

But the bones and joints alone would not enable us to move in all the various directions we desire; therefore nature has provided us with a great many different muscles for this purpose, as well as to give form and proportion to the body.

57. The following cut represents a man with the muscles which cover the bones, without the skin. The muscle is what we call lean meat. Do not forget, children, when you eat beef-steak, that you are eating the muscles of the ox, which keep his bones together, and enable him to draw the great loads. The muscles are red because they contain blood.

58. They cover the bones, crossing the joints, running along up the limbs, over the back, arms, and neck, and are particularly large and numerous where they are most needed, as in the back, hips, legs, etc., and though

56. By what are the bones covered? What is the rheumatism? Do the joints rub together? What enables them to move easily? What would be the result if the bones were not moistened? What is necessary beside bones and joints for all our motions? What is the office of the muscles? 57. What is represented by the cut? What is muscle? What are the muscles of the ox? Why are the muscles red? 58. How numerous are the muscles?

so numerous they never interfere with each other. Sometimes the action of a muscle is needed where, if it

Now

were placed, it would be quite inconvenient. mark the remedy. We could not have devised a better or more ingenious one if we had bestowed a great deal

58. Is the action of muscles ever required where their position would be inconvenient? How is this remedied?

of thought on the subject. The body of the musclewhich means the centre of the muscle, and is generally the largest part-is placed at a proper distance, and made to communicate, where the action is necessary, by slender strings or threads.

59. As every joint in the fingers, hands, and feet are moved by muscles, if the muscles had been placed in the palm or back of the hand, or in the feet, they would have been very unsightly, and very clumsy in appearance. They are, however, situated in the arm, and act by long strings called tendons, which pass to the joints. These tendons are all clasped down at the wrist by a bracelet which nature has prepared under the skin to keep them in their place. In the same manner the muscles which move the toes and feet are placed along the leg, and are all confined by a little band at the ankle.

60. Without this wise provision the tendons would have sprung from their places every movement we made. Whatever part of the body we examine, we see the wisdom and goodness of our Creator; every part is so nicely fitted and adapted to the purpose for which it is used.

Where there is a muscle needed, there we find it arranged in the most convenient and beautiful manner. Suppose instead of the joint at the shoulder we had had the hinge-joint, like the one at the arm, then we could

58. What is the body of the muscle? 59. Where are the muscles which move the hands and feet situated? Why are they not placed in the hands or feet? How are the tendons confined at the wrist? How are they confined at the ankle? 60. What would take place if they were not bandaged? What do we see displayed in every part of the body What adaptation is there in the body?