In the rachitic bone all these processes of growth and the maintenance of equilibrium are abnormal. Calcium salts are not deposited in a normal way. In a normal bone the junction of the cartilage with the shaft forms a straight, regular line. In the rachitic bone it is ragged because there is no provisional zone of calcification and the cartilage is invaded by large tufts of blood-vessels from the shaft which destroy it irregularly. At the same time masses of cartilage persist where they should be destroyed and islands remain cut off from the main body of the tissue. Osteoid is not calcified as it is formed either in the trabecular or by the periosteum, so that the bones become soft. The animal attempts unsuccessfully to compensate for the weakness due to the lack of lime salts by producing osteoid tissue in abnormal amounts, especially at points subject to stress and strain (the curved side of the bone and at the insertions of muscle and tendons). This over-production of osteoid and cartilage causes irregular enlargement of the bones and their weakness consequent upon the lack of lime salts results in bowing and fracture. Because of the abnormal growth at the end of the shaft a zone known as the rachitic metaphysis forms, which consists of blood-vessels, connective tissue, osteoid, marrow elements, and cartilage cells in all stages of degeneration and change into other tissue. The osteoid formed shows little sign of being absorbed in rickets as it is commonly seen. The balance of forces has swung in the direction of apposition and persistence of cartilage.