. The anatomy of the domestic animals. Veterinary anatomy. STRUCTURE OF BONES 21 STRUCTURE OF BONES' Bones consist chiefly of bone tissue, Init considered as organs they present also an enveloping membrane, termed the periosteum, the marrow, vessels, and nerves. The architecture of bone can be studieil best by means of longitudinal and transverse sections of specimens which have been macerated so as to rt'mo\'e most of the organic matter. These show that the l)one consists of an external shell of dense compact sub- stance, within which is the more loosely arranged spongy substance. In typical
. The anatomy of the domestic animals. Veterinary anatomy. STRUCTURE OF BONES 21 STRUCTURE OF BONES' Bones consist chiefly of bone tissue, Init considered as organs they present also an enveloping membrane, termed the periosteum, the marrow, vessels, and nerves. The architecture of bone can be studieil best by means of longitudinal and transverse sections of specimens which have been macerated so as to rt'mo\'e most of the organic matter. These show that the l)one consists of an external shell of dense compact sub- stance, within which is the more loosely arranged spongy substance. In typical long bones the shaft is hollowed to form the medullary cavity (Cavmn medullare). The compact substance (Substantia compacta) differs greatly in thickness in various situations, in conformity with the stresses and strains to which the bone is subjected. In the long bones it is thickest in or near the middle part of the shaft and thins out toward the extremities. On the latter the layer is very thin, and is especially dense and smooth on joint surfaces. The spongy substance (Substantia spongiosa) consists of delicate bony plates and spicules which run in various directions and intercross. These are definitely arranged with regard to mechanical re- quirements, so that systems of pressure and tension jjlates can be recognized, in conformity with the lines of pressure and the pull of tendons and liga- ments respectively. The intervals between the ]3lates are occupied by marrow, and are termed marrow spaces (Ccllulse metlullares). The spongy substance forms the bulk of short bones and of the extremities of long bones; in the latter it is not con- fined to the ends, but extends a variable distance along the shaft also. Some bones contain air-spaces within the compact substance instead of spongy lione and marrow, and hence are called pneumatic bones (Ossa pneumatica). These ca\'ities are termed sinuses, and are lined with mucous membrane; they communicate indirectly ivith the external
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Keywords: ., bo, bookcentury1900, bookdecade1910, booksubjectveterinaryanatomy
