PATHOLOGY OF THE DISORDERS OF GROWTH Several factors, biological as well as pathological, contribute to these changes. The bony skeleton which was originally planned to assume the position of a quadruped had to overcome many obstacles before it changed and adapted itself to the new surroundings. Some of these difficulties we have already mentioned in the discussion of congenital dislocation of the hip, and these manifest themselves at that period of life when the body commences to rise from the horizontal position.
The vertebral column, pelvis, and lower extremities are especially affected by the weight. This being a critical stage in the development of both the soft tissues and bony structures, disturbances in their future growth increase so much the more if the building material undergoes pathological changes.
Rachit is should be mentioned as one of the chief causes of disturbance at this period. In this disease the building material is changed into softer tissue and the solidity and resistive power of the bony skeleton are im paired by a pathological process, the result being that the bones become curved following the direction of the weight-bearing or of muscular action.
On the other hand, the formation of new bone tissue appears inter rupted, the epiphyses are thickened and the longitudinal growth is delayed and distorted. The deformity of the bones combined with a diseased and flattened condition of the joints and ligaments, and also with marked atrophy of the muscular tissue, produces the typical pic ture of rachitis. This disease, starting in early infancy, continues through the first years of life and is a constant menace to growth and further development. Traces are manifest in later years of childhood, and at puberty it appears as the so-called rachitis tarda at a time when the body consumes a vast amount of energy as it is undergoing revolu tionary changes. This decreases the resistive power of the body against disease at a time when the child's life and surroundings demand it in a much higher degree.
All deformities which are observed during the first and second childhood result from a combination of these factors. They pertain chiefly to the bones of the trunk and of the apparatus of locomotion.