Hygienic Physiology | Page 9

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