BONE

is the hard substance of which the skeletons of animals is built up, serving as a framework for the body and for the protection of vital parts, and is a connective ti ue in which earthy salts have been deposited in order to strengthen the structure. B’s are cla ed as long (e.g.), in thigh, flat, (e.g.), in, and cutical or irregular (e.g.), {n wrist. The animal or organic matter amounts in b. to about one-third of the whole, and the earthy or organic matter, in the form of salts, to about two-thirds. According as it is dense and hard in structure, or light and spongy, b. is called compact or cancellous. On micro-| scopic examination b. is found to be formed by innumerable little canals, running longitudinally in a long b., each containing blood ve els, and their walls formed by a series of rings of bony substance. Filling the spaces in b. is marrow, composed of fat cells, and of the same corpuscular elements as are found in the blood (q.v.), but in a le advanced stage of development; there are two kinds of marrow, yellow and red, the former being found in the interior of long bones (e.g.), the thigh bone, and the latter in smaller long bones (e.g.), the ribs, and in short bones (e.g.), vertebrae. Yellow marrow has a much greater number of fat cells, hence its color, while red marrow is almost entirely composed of the other cellular elements, from which the blood corpuscles are formed. B. is formed from cartilage or from membrane, usually the former, little points of bony cells developing and the area then spreading. Inflammation may affect the covering of the b. or periosteum, the b. itself, or the substance in the canal within, or medulla. It may be acute or chronic, the ‘acute form usually being due to injury followed by bacterial infection, and the chronic to the continued suppuration of acute form, to syphilis, and to tuberculosis. The former is usually treated by rest and fomentations, operation being sometimes nece ary, and the latter by general treatment of the disease affecting the individual. Fractures are treated by rest in splints, and ma age, begun early. ktickets is a general disease of chilper with special manifestations in the ones,