In entering upon a description of the human body, our attention is naturally directed first to the BONES. Osteology, or that branch of anatomy which treats of the bones, is of more importance to the surgeon, the physician, and natural historian, than is generally ima gined ; and has been regarded by the most eminent ana tomists, as the foundation on which the whole structure of the science must be raised. The bones vary in num ber, appearance, and texture, according to their age. At birth, many of them are soft, flexible, transparent ; containing no osseous matter ; but divided into several portions, which are afterwards to be united in their pro gress to maturity. In the full-grown subject, they are the firmest, hardest and most solid part., of the whole body ; all of them are permanent except the first crop of teeth, which are shed at an early period; and when the whole are ossified, they amount, in the human sub ject, to about two hundred and forty.
As they give form and stability to the body, they must, of course, be in some manner connected with each other. Accordingly, they are generally found connected by unequal surfaces, whose cavities and eminences mu tually correspond. Of these joinings, which are called articulations, there are so many that they have never been enumerated. They are divided into classes of three different kinds. The first kind admits of a free, easy, and conspicuous motion ; the motion of the second is rather obscure ; the third has no motion, or at least it is imperceptible. These classes, with their varieties, or particular species, are in all about nine.
As the roughness of the bones, however, would pre vent them from moving freely without much friction, in all cases where motion occurs there must be some in tervening substance to obviate this inconvenience. In the recent subject, accordingly, we invariably find, that all those articulating surfaces, which are liable to mo tion, are covered with a smooth elastic substance, of a pearl colour, known, in common language, by the name of gristle, and in anatomy by that of cartilage. To ren der the motion still easier, the cartilage is lubricated by a fluid, called synovia ; which is of the same service to the different joints that oil is to a piece of machinery. These articulations, alone, however, would be insuffi cient either to regulate the motion of the bones, or to preserve them in their situation. The bones must therefore be connected by sonic intermediate substance. Cartilage forms sometimes the link of connection, but, besides cartilage, there are three other connecting sub stances—ligaments, membranes, and flesh. Ligaments
arc strong flexible substances, of a fibrous texture, whi tish, glistening, and of little elasticity. Their forms, situations, and uses, are extremely various. With re spect to the bones, they arc generally placed on the outside of the articulation, and secure the parts by their great strength and vigorous adhesion. So important is the knowledge of these ligaments in the practice of surgery, and in explaining many symptoms which occur in the joints from disease or accident, that a separate branch of anatomy has been appropriated to them, un der the name of Sydesmology. The particular ligaments have not been enumerated ; but reckoning classes some times as pairs, those which have been described and named are about an hundred.
The membranes, the next connecting substance, when they surround the extremities of the bones, and contri bute to the security of the joints, are called capsular ligaments. Membranes, in general, are thin webs of a whitish colour, more flexible and elastic than ligaments. Besides contributing to the security of the joints, and facilitating their movement, they answer many other very important purposes. They line all the external cavities; they surround every organ in the body ; and while they unite the whole together, they at the same time secure the separate and peculiar motion of each part; making it sometimes to conspire with the whole, and sometimes to act as distinct and independent. They frequently vary in strength, texture, and appearance, and have different names, according to their different positions. Two within the cranium are called matres; some which inclose bundles of flesh are called aponeu roses ; the membrane which lines the cavity of the breast, and surrounds its viscera, is termed pleura ; that which surrounds the cavity of the abdomen and its vis cera is denominated peritoneum ; those which surround bones arc styled periostea, and those which surround cartilages, perichondria; when they surround any other organ, they are generally called tunicm, or coats.
The other substance which connects the bones is flesh. The fore-legs, or, in the language of anatomy, the su perior extremities of many quadrupeds, adhere chiefly by this connection to the rest of the system. This sub stance, indeed, contributes to the security of all the joints, although its principal use is widely different, and much more important.