bone of the forearm, on the contrary, is small at its upper end, while it is large at its lower end, where it forms the wrist joint. At the elbow, the head of the radius is convex and fits into a shallow cavity in the ulna, while at the wrist the ulna plays in a similar socket in the radius. Thus the radius may roll over and even cross the ulna.

THE WRIST, or _carpus_, consists of two rows of very irregular bones, one of which articulates with the forearm; the other, with the hand. They are placed side to side, and so firmly fastened as to admit of only a gliding motion. This gives little play, but great strength, elasticity, and power of resisting shocks.

THE HAND.--The _metacarpal_ (_meta_, beyond; _karpos_, wrist), or bones of the palm, support each a thumb or a finger. Each finger has three bones, while the thumb has only two. The first bone of the thumb, standing apart from the rest, enjoys a special freedom of motion, and adds greatly to the usefulness of the hand.

FIG. 12.

[Illustration: _Bones of the Hand and the Wrist._]

The first bone (Figs. 11, 12) of each finger is so attached to the corresponding metacarpal bone as to move in several directions upon it, but the other phalanges form hinge joints.

The fingers are named in order: the thumb, the index, the middle, the ring, and the little finger. Their different lengths cause them to fit the hollow of the hand when it is closed, and probably enable us more easily to grasp objects of varying size. If the hand clasps a ball, the tips of the fingers will be in a straight line.

The hand in its perfection belongs only to man. Its elegance of outline, delicacy of mold, and beauty of color have made it the study of artists; while its exquisite mobility and adaptation as a perfect instrument have led many philosophers to attribute man's superiority even more to the hand than to the mind. [Footnote: How constantly the hand aids us in explaining or enforcing a thought! We affirm a fact by placing the hand as if we would rest it firmly on a body; we deny by a gesture putting the false or erroneous proposition away from us; we express doubt by holding the hand suspended, as if hesitating whether to take or reject. When we part from dear friends, or greet them again after long absence, the hand extends toward them as if to retain, or to bring them sooner to us. If a recital or a proposition is revolting, we reject it energetically in gesture as in thought. In a friendly adieu we wave our good wishes to him who is their object; but when it expresses enmity, by a brusque movement we sever every tie. The open hand is carried backward to express fear or horror, as well as to avoid contact; it goes forward to meet the hand of friendship; it is raised suppliantly in prayer toward Him from whom we hope for help; it caresses lovingly the downy cheek of the infant, and rests on its head invoking the blessing of Heaven,--_Wonders of the Human Body_.]

FIG. 13.

[Illustration: _The Mechanism of the Hip Joint._]

2. THE LOWER LIMBS.--THE HIP--The thigh bone, or _femur_, is the largest and necessarily the strongest in the skeleton, since at every step it has to bear the weight of the whole body. It articulates with the hip bone by a ball-and-socket joint. Unlike the shoulder joint, the cup here is deep, thus affording less play, but greater strength. It fits so tightly that the pressure of the air largely aids in keeping the bones in place. [Footnote: In order to test this, a hole was bored through a hip bone, so as to admit air into the socket, the thigh bone at once fell out as far as the ligaments would permit. An experiment was also devised whereby a suitably prepared hip joint was placed under the receiver of an air pump. On exhausting the air, the weight of the femur caused it to drop out of the socket, while the readmission of the air raised it to its place. Without this arrangement, the adjacent muscles would have been compelled to bear the additional weight of the thighbone every time it was raised. Now the pressure of the air rids them of this unnecessary burden, and hence they are less easily fatigued--WEBER] Indeed, when the muscles are cut away, great force is required to detach the limbs.

THE KNEE is strengthened by the patella_, or kneepan (_patella_, little dish), a chestnut-shaped bone firmly fastened over the joint.

The shin bone, or _tibia_, the large, triangular bone on the inner side of the leg, articulates both with the femur and the foot by hinge joints. The kneejoint is so made, however, as to admit of a slight rotary motion when the limb is not extended.

The _fibula_ (_fibula_, a clasp), the small, outside bone of the leg, is firmly bound at each end to the tibia. (See Fig. 1.) It is immovable, and, as the tibia bears the principal weight of the body, the chief use of this second bone seems to be to give more surface to which the muscles may be attached. [Footnote: A young man in the hospital at Limoges had lost the middle part of his tibia. The lost bone was not reproduced, but the fibula, the naturally weak and slender part of the leg, became thick and strong enough to support the whole body.--STANLEY'S _Lectures_.]

THE FOOT.--The general arrangement of the foot is strikingly like that of the hand (Fig. 1). The several parts are the _tarsus_, the _metatarsus_, and the _phalanges_. The graceful arch of the foot, and the numerous bones joined by cartilages, give an elasticity to the step that could never be attained by a single, flat bone. [Footnote: The foot consists of an arch, the base of which is more extended in front than behind, and the whole weight of the body is made to fall on this arch by means of a variety of joints. These joints further enable the foot to be applied, without inconvenience, to rough and uneven surfaces.--HINTON.] The toes naturally lie straight forward in the line of the foot. Few persons in civilized nations, however, have naturally formed feet. The big toe is crowded upon the others, while crossed toes, nails grown-in, enormous joints, corns, and bunions abound.

THE CAUSE OF THESE DEFORMITIES is found in the shape and size of fashionable boots and shoes. The sole ought to be large enough for full play of motion, the uppers should not crowd the toes, and the heels should be low, flat, and broad. As it is, there is a constant warfare between Nature and our shoemakers, [Footnote: When we are measured for boots or shoes, we should stand on a sheet of paper, and have the shoemaker mark with a pencil the exact outline of our feet as they bear our whole weight. When the shoe is made, the sole should exactly cover this outline.] and we are the victims. The narrow point in front pinches our toes, and compels them to override one another; the narrow sole compresses the arch; while the high heel, by throwing all the weight forward on the toes, strains the ankle, and, by sending the pressure where Nature did not design it to fall, causes that joint to become enlarged. The body bends forward to meet the demand of this new motion, and thus loses its uprightness and beauty, making our gait stiff and ungraceful. (See p. 271.)

DISEASES, ETC.--l. _Rickets_, a disease of early life, is caused by a lack of mineral matter in the bones, rendering them soft and pliable, so that they bend under the weight of the body. They thus become permanently distorted, and of course are weaker than if they were straight, [Footnote: Just here appears an exceedingly beautiful provision. As soon as the disproportion of animal matter ceases, a larger supply of mineral is sent to the weak points, and the bones actually become thicker, denser, harder, and consequently stronger at the very concave part where the stress of pressure is greatest.--WATSON'S _Lectures_. We shall often have occasion to refer to similar wise and providential arrangements whereby the body is enabled to remedy defects, and to prepare for accidents.] Rickets is most common among children who have inherited a feeble constitution and who are ill fed, or who live in damp, ill-ventilated houses. "Rickety" children should have plenty of fresh air and sunlight, nourishing food, comfortable clothing, and, in short, the best of hygienic care.

2. _A Felon_ is a swelling of the finger or thumb, usually of the last joint. It is marked by an accumulation beneath the periosteum and next the bone. The physician will merely cut through the periosteum, and let out the effete matter.

3. _Bowlegs_ are caused by children standing on their feet before the bones of the lower limbs are strong enough to bear their weight. The custom of encouraging young children to stand by means of a chair or the support of the hand, while the bones are yet soft and pliable, is a cruel one, and liable to produce permanent deformity. Nature will set the child on its feet when the proper time comes.

4. _Curvature of the Spine_.--When the spine is bent, the packing between the vertebræ becomes compressed on one side into a wedge-like shape. After a time, it will lose its elasticity, and the spine will become distorted. This often occurs in the case of students who bend forward to bring their eyes nearer their books, instead of lifting their books nearer their eyes, or who raise their right shoulder above their left when writing at a desk which is too high. Round shoulders, small, weak lungs, and, frequently, diseases of the spine are the consequences. An erect posture in reading or writing conduces not alone to beauty of form, but also to health of body. We shall learn hereafter that the action of the muscles bears an important part in preserving the symmetry of the spine. Muscular strength comes from bodily activity; hence, one of the best preventives of spinal curvature is daily exercise in the open air.

5. _Sprains_ are produced when the ligaments which bind the bones of a joint are strained, twisted, or torn from their attachments. They are quite as serious as a broken bone, and require careful attention lest they lead to a crippling for life. By premature use a sprained limb may be permanently impaired. Hence, the joint should be kept quiet, even after the immediate pain is gone.

6. _A Dislocation_ is the forcible displacement of a bone from its socket. It is, generally, the result of a fall or a violent blow. The tissues of the joint are often ruptured, while the contraction of the muscles prevents the easy return of the bone to its place. A dislocation should be reduced as soon as possible after the injury, before inflammation supervenes.

PRACTICAL QUESTIONS.

1. Why does not a fall hurt a child as much as it does a grown person?

2. Should a young child ever be urged to stand or walk?

3. What is meant by "breaking one's neck"?

4. Should chairs or benches have straight backs?

5. Should a child's feet be allowed to dangle from a high seat?

6. Why can we tell whether a fowl is young by pressing on the point of the breastbone?

7. What is the use of the marrow in the bones?

8. Why is the shoulder so often put out of joint?

9. How can you tie a knot in a bone?