File:The cat - an introduction to the study of backboned animals, especially mammals (1881) (20398600728).jpg

Title: The cat : an introduction to the study of backboned animals, especially mammals
Identifier: catintroduction00miva (find matches)
Year: 1881 (1880s)
Authors: Mivart, St. George Jackson, 1827-1900
Subjects: Cats; Anatomy, Comparative
Publisher: New York : Scribner's
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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20 THE CAT. (CHAP. II. adjacent lacunae unite, and thus fluid can traverse every part of the bone. The Haversian canals grow larger as they proceed inwards (in such a bone as that of the thigh,) and open into still larger channels and yet wider interspaces which are called cancelli, ultimately merging into a hollow central part called the medullary cavity of the bore because it contains that delicate fibrous tissue and fat which constitutes marrow, as already mentioned. Some bones have their entire substance replete with cavities or cancelli, and such are called cancellated or spongy. § 6. Ossification may take place either through pre-existing carti- lage or through membrane, and in either case blood-vessels advance into the pre-existing ma- he terial, and therewith that material is absorbed and disappears around them and is replaced by calcareous substance. The lacunae are inter- spaces which have been left uncalcified owing to the presence there of certain cells. These cells have sent out radiating processes (like some of the connective-tissue cells, as already noticed,) which have also escaped the general calcification of the intercellular substance, and thus the canaliculi have been produced. Thus contents of the lacunae are truly bone-cells or corpuscles. Bone tissue therefore is, except as to its calcareous nature, very like connec- tive tissue and cartilage. The bony substance answers to the matrix of these other tissues, and the "bone cells" to their corpuscles. When the earthy matter of bone is dissolved their original cellular contents may often be detected. When a bone ossifies from cartilage, as all thick bones do, the deposit begins in the form of opaque granules of calcareous matter, which vertical Section of surround and sometimes invade the cartilage at's thighbone (Femur), capsules and form a dense and irregular osseous heTdngof1h7t?r(s4f Se tissue, without lacunas or canaliculi. Spaces are great trochanter (<e), and of then formed in this substance by absorption, its distal end (le). . . p , , . l A • and it these spaces JargeJy accumulate, can- cellated tissue is formed. The spaces may, however, become filled with a fresh and secondary deposit of bone in concentric rings round the blood-vessels, thus forming the " compact bone " already described. When bone is formed from membrane, it assumes the compact form, with lacunae and canaliculi, at once, and is not preceded by granular deposit. § 7. The growth of bone takes place in various ways by the ossi- fication of the inner layer of the periosteum surrounding it. In long bones, which are preceded by cartilage, the ends remain for some
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