The diseases of infants and children . as in Fig. 196. is not due to an abnormal production of cartilage but to a failure of itto be transformed into bone in the normal manner (Schmorl). ^ The layersof cartilage are transversed irregularly by canals containing much-dilatedblood-vessels and soft, vascular, imperfectly formed osteoid tissue,deficient in lime-salts. The zones of calcification and, last, of ossification, 1 Loc. cit, 424. RACHITIS 589 are broader than in healthy bone and have lost their normal, sharply-defined outlines, exhibiting instead calcified areas irregularly mingledwith oth
The diseases of infants and children . as in Fig. 196. is not due to an abnormal production of cartilage but to a failure of itto be transformed into bone in the normal manner (Schmorl). ^ The layersof cartilage are transversed irregularly by canals containing much-dilatedblood-vessels and soft, vascular, imperfectly formed osteoid tissue,deficient in lime-salts. The zones of calcification and, last, of ossification, 1 Loc. cit, 424. RACHITIS 589 are broader than in healthy bone and have lost their normal, sharply-defined outlines, exhibiting instead calcified areas irregularly mingledwith others still cartilaginous, and with scattered, unusually largemedullary spaces containing osteoid tissue. This disappearance of thesharply-defined junctions of the zones, as seen in the normal epiphysis,with the irregular inroads of one into the other, is one of the most strikingcharacteristics of rickets. The spongy portion of the shaft exhibitsincreased vascularity, with erosion of the trabeculae, resulting in large,medullary Fig. 198.—Skeleton of a Severe Case of a negro child of 6 years, in the Pennsylvania Hospital of Philadelphia at the timeof his death. (Donhauscr, Bull, of Ayer Clinical Laboratory, 1907, -Vo. 4, 13.) Beneath the periosteum of both long and flat bones an analogousprocess is seen, with cell-proliferation, vascularity, and imperfect calcifi-cation, resulting in thickening and in the production of osteoid tissue. Chemically the rachitic osseous tissue is very decidedly altered in theamount of lime and of phosphorus contained, these being sometimesdiminished to 50 per cent, or even 25 per cent, of the normal. Thepercentage of organic matter and of water is increased. These character-istics account for the unusual degree of softness and flexibility of thebones, which suffer in consequence from green-stick fractures, with theproduction of a large amount of callus. 590 THE DISEASES OF CHILDREN During recovery from the disease the bony chan
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