Читать книгу A Treatise on Domestic Economy; For the Use of Young Ladies at Home and at School - Beecher Catharine Esther - Страница 8

The bones are the most solid parts of the body. They are designed to protect and sustain it, and also to secure voluntary motion. They are about two hundred and fifty in number, (there being sometimes a few more or less,) and are fastened together by cartilage, or gristle, a substance like the bones, but softer, and more elastic.

In order to convey a more clear and correct idea of the form, relative position, and connection, of the bones constituting the human framework, the engraving on page 70, (Fig. 1,) is given.

Fig. 1.

By the preceding engraving, it will be seen, that the cranium, or skull, consists of several distinct pieces, which are united by sutures, (or seams,) as represented by the zigzag lines; a, being the frontal bone; b, the parietal bone; c, the temporal bone; and d, the place of the occipital bone, which forms the back part of the head, and therefore is not seen in the engraving. The nasal bones, or bones of the nose, are shown at e; f, is the cheek bone; g, the upper, and h, the lower, jaw bones; i, i, the spinal column, or back bone, consisting of numerous small bones, called vertebræ; j, j, the seven true ribs, which are fastened to the spine, behind, and by the cartilages, k, k, to the sternum, or breast bone, l, in front; m, m, are the first three false ribs, which are so called, because they are not united directly to the breast bone, but by cartilages to the seventh true rib; n, n, are the lower two false, which are also called floating, ribs, because they are not connected with the breast bone, nor the other ribs, in front; o, o, p, q, are the bones of the pelvis, which is the foundation on which the spine rests; r, r, are the collar bones; s, s, the shoulder blades; t, t, the bones of the upper arm; u, u, the elbow joints, where the bones of the upper arm and fore arm are united in such a way that they can move like a hinge; v w, v w, are the bones of the fore arm; x, x, those of the wrists; y, y, those of the fingers; z, z, are the round heads of the thigh bones, where they are inserted into the sockets of the bones of the pelvis, giving motion in every direction, and forming the hip joint; a b, a b, are the thigh bones; c, c, the knee joints; d e, d e, the leg bones; f, f, the ankle joints; g, g, the bones of the foot.

The bones are composed of two substances,—one animal, and the other mineral. The animal part is a very fine network, called the 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; making the bones more brittle than in earlier life.

As we shall soon have occasion to refer, particularly, to the spinal, or vertebral column, and the derangement to which it is liable, we give, on page 72, representations of the different classes of vertebræ; viz. the cervical, (from the Latin, cervix, the neck,) the dorsal, (from dorsum, the back,) and lumbar, (from lumbus, the loins.)

Fig. 2.

Fig. 2, represents one of the cervical vertebræ. Seven of these, placed one above another, constitute that part of the spine which is in the neck.

Fig. 3.

Fig. 3, is one of the dorsal vertebræ, twelve of which, form the central part of the spine.

Fig. 4.

Fig. 4, represents one of the lumbar vertebræ, (five in number,) which are immediately above the sacrum. These vertebræ are so fastened, that the spine can bend, in any direction; and the muscles of the trunk are used in holding it erect, or in varying its movements.

By the drawings here presented, it will be seen, that the vertebræ of the neck, back, and loins, differ somewhat in size and shape, although they all possess the same constituent parts; thus, A, in each, represents the body of the vertebræ; B, the articulating processes, by which each is joined to its fellow, above and below it; C, the spinous process, or that part of the vertebræ, which forms the ridge to be felt, on pressure, the whole length of the centre of the back. The back bone receives its name, spine, or spinal column, from these spinous processes.

It is the universal law of the human frame, that exercise is indispensable to the health of the several parts. Thus, if a blood-vessel be tied up, so as not to be used, it shrinks, and becomes a useless string; if a muscle be condemned to inaction, it shrinks in size, and diminishes in power; and thus it is also with the bones. Inactivity produces softness, debility, and unfitness for the functions they are designed to perform. This is one of the causes of the curvature of the spine, that common and pernicious defect in the females of America. From inactivity, the bones of the spine become soft and yielding; and then, if the person is often placed, for a length of time, in positions that throw the weight of the body unequally on certain portions of the spine, they yield to this frequent compression, and a distortion ensues. The positions taken by young persons, when learning to write or draw, or to play on the guitar, harp, or piano, and the position of the body when sleeping on one side, on high pillows, all tend to produce this effect, by throwing the weight of the body unequally, and for a length of time, on particular parts of the spine.

Fig. 5.