THE VERTEBRAL COLUMN 523 



Curvatures of the Vertebral Column. In the foetus 

 the vertebral column shows two primary curves, both concave 

 forwards. Of these, one extends from the head to the pelvis 

 and the other affects the sacral region. When the child begins 

 to sit up and elevate its head, a forward convexity appears in 

 the cervical region ; and, when the erect attitude is assumed 

 and the child begins to walk, a forward convexity appears in 

 the lumbar region also. The development of these secondary 

 curves enables the vertebral column to transmit the weight of 

 the trunk to the pelvis in such a way that little or no muscular 

 effort is required to maintain the erect attitude. 



The amount of movement possible between any two adjoining 

 vertebrae is very small, but by the summation of these movements 

 aided by the compressibility of the intervertebral fibre-cartilages, 

 the vertebral column, as a whole, acquires a moderately extensive 

 range of movement. In flexion and extension of the vertebral 

 column the lumbar and cervical regions move more freely than 

 the thoracic region, but the reverse is the case with regard to 

 rotation, except in the case of the joints between the atlas and 

 the second cervical vertebra. Lateral flexion occurs chiefly in 

 the lumbar region. 



In weakly children and debilitated adolescents, the body 

 may grow more rapidly than the muscles which support it. 

 These patients instinctively adopt attitudes which relieve the 

 tired muscles and throw the strain on the ligaments of the 

 intervertebral joints. The habitual adoption of such attitudes 

 causes overstretching of the ligaments on which the strain is 

 thrown, and the opposing ligaments become shortened. There 

 is, therefore, a tendency for the faulty attitude to be maintained 

 mechanically. When the proper alignment of the vertebral 

 column is altered, the muscular balance is upset. One group of 

 muscles obtains a mechanical advantage over the corresponding 

 antagonistic group, which consequently becomes overstretched. 

 As a result, abnormal curves appear in the vertebral column. 



Lateral Curvature, or Scoliosis, occurs primarily in the 

 thoracic region and its convexity is usually directed to the 

 right side. Compensatory curves, which are convex in the 

 opposite direction, appear above and below the primary curve, 

 and they serve to maintain the equilibrium of the body. The 

 lateral curvature of the thoracic region is not produced by true 

 lateral flexion of the vertebral column, as this movement is 

 restricted to the lumbar region. The thoracic vertebrae become 



