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ANATOMY AND PHYSIOLOGY OF 



munication is established between the dense 

 and soft parts. The periosteum is anal- 

 agous to the fibrous textures, being com- 

 posed of numerous inelastic fibres of great 

 strength and density. 



The inner surface of the periosteum is 

 connected with the bone by the vessels pass- 

 ing from the one to the other, and also by 

 numerous prolongations, which pervade the 

 osseous substance. 



The blood-vessels of the periosteum are 

 numerous, and are easily demonstrated by 

 injection. 



CARTILAGE.* 



The structure which appears most inti- 

 mately connected with the osseous is carti- 

 lage. It is a firm and dense substance, 

 apparently homogeneous in its texture, semi- 

 pellucid, and of a milk-white or pearly color. 



The surface of cartilage is smooth and 

 uniform, presenting neither eminences nor 

 cavities, pores nor inequalities. It has, 

 however, minute capillary vessels, the diam- 

 eters of which are too small for ocular 

 demonstration. Notwithstanding its den- 

 sity, it has a minute circulating apparatus, 

 which is demonstrated in diseases known 

 as spavin and ringbone, in which absorp- 

 tion of cartilage occurs. 



Cartilaginous structures are chiefly com- 



* " The mechanical property which particularly distin- 

 guishes cartilage is elasticity, a quality wliich it possesses 

 in a greater degree than any other animal structure, and 

 which adapts it to many useful purposes in the economy. 

 Hence it forms the basis of many parts where, contrary to 

 the purposes answered by the bones, pliancy and resistance 

 as well as firmness are required ; and hence cartilage is 

 employed when a certain shape is to be preserved, to- 

 gether with a capability of yielding to an external force. 

 The flexibility of cartilage, however, docs not extend 

 beyond certain limits ; if these be exceeded, fracture takes 

 place. Great density bestowed upon an animal structure, 

 indeed, appears to be in all cases attended with a propor- 

 tionate degree of brittleness. These mechanical proper- 

 ties of cartilages, as well as their intimate structure, 

 although nearly homogenous in all, are subject to modifi- 

 cation in different kinds of cartilage. Cartilages are 

 covered with a fine membrane, termed the perichondrium, 

 analogous in its structure and office to the periosteum, 

 which we have already had occasion to point out among 

 the fibrous membranes, as investing the bones." — Ror/et. 



posed of gelatin, albumen, and phosphate 

 of calcis. 



Cartilage occurs in two forms, temporary 

 and permanent. The former prevails pre- 

 vious to adult life ; the latter are identical 

 with the permanent structures after the 

 animal has migrated from colthood. 



There are three or four different forms of 

 cartilages, viz : the membriform, interosseal, 

 articular, and inter-articular. 



The membriform are fibro-cartilaginous ; 

 they furnish a basis of support to the softer 

 parts, supply the place of bone, and give 

 form, shape, and firmness, to parts unossi- 

 fied. By their elasticity, they admit of con- 

 siderable variation of figure and form, yield 

 to external pressure, and recover their proper 

 shape as soon as pressure is removed. This 

 kind of cartilage is found in the nostrils, 

 ears, larynx, and trachea. 



The interosseal cartilages pass from one 

 bone to another, adhering firmly by their 

 extremities to each. They permit of an 

 increase of extent or motion, as observed 

 between the ribs ; when macerated, they are 

 divisable into laminae of an oval shape, 

 which are united by fibres passing obliquely 

 between them. 



The articular cartilages are those plates 

 of articular substance which adhere firmly 

 and inseparably to the surfaces of bones 

 which are opposed to each other in the 

 joints, or over which tendons and ligaments 

 play. The elastic resistance of this carti- 

 lage has a powerful tendency to lessen the 

 shocks incident to sudden and violent 

 actions. 



The inter-articular cartilages do not dif- 

 fer in composition from the preceding. 

 They are attached to the inside of the cap- 

 sular ligament, by which they are rendered 

 somewhat movable ; and, being interposed 

 between the bones of the knee and hock, 

 allow them a greater latitude of motion, 

 while at the same time they contribute to 

 adapt their surfaces more perfectly to each 

 other 

 laminated 



The structure of these cartilages is 



