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The disadvantages resulting from the want of alternate curvatures in 

 the vertebral column of the child, is further increased, by the total ab- 

 sence of spinous processes. It is well known, that the principal use of 

 these projections, is to place the power at a distance from the^ centre of 

 motion of the vertebrae, to increase the length of the lever by which it 

 acts in straightening the trunk, and thereby to render its action more effi- 

 cacious. At the period of birth, the vertebrae have no spinous processes, 

 they afterwards grow from the. place at which the lamina of those bones 

 are united, by means of a .cartilaginous substance, which completes 

 the posterior part of the vertebral canal. The muscles destined to keep 

 the trunk erect, weakened by its constant flexion during gestation, lose, 

 besides, a great deal of their power, from the unfavourable manner in 

 which they are applied to the part on which they .are to act. 



The flexion of the head does not depend merely on its very considerable 

 \veight, but, likewise, on the want of spinous processes in the cervical 

 vertebrae; since the principal motions of the neck are performed, not so 

 much by articulation with the atlas, as by union of the other cervical 

 vertebrae. 



The pelvis of the child is but imperfectly evolved, and its upper outlet 

 very oblique. The viscera, which are afterwards to be contained within 

 its cavity, are, for the greater part, situated above it. This obliquity of 

 the pelvis would require a perpetual straightening of the vertebral column 

 to prevent the direction of the centre of gravity from obeying its natural 

 tendency forward. On the other hand, the vertebral column resting on a 

 narrow pelvis, is less firmly fixed, and may more readily be drawn beyond 

 the limits of the base of sustentation. Lastly, the limited extent of the 

 pelvis, together with its obliquity, causes the ill supported abdominal 

 viscera to fall on the anterior and inferior part of the parietes of the ab- 

 domen, and favours the fall of the body in the same direction. 



The patella, which answers the double purpose of giving firmness to 

 the knee joint, in front of which it is placed, and of increasing the power 

 of the muscles of the leg, by placing them at a distance from the centre of 

 motion in that articulation, and by increasing the angle at which they are 

 inserted into the tibia, as yet does not exist in new-born children. The 

 tendinous portion of the leg, where the patella is hereafter to be formed, 

 is merely of a more condensed tissue, and of a cartilaginous hardness. 



The want of a fulcrum is attended with a continual disposition in the 

 leg to bend upon the thigh, and the parallel direction of its extensor 

 muscles, occasions a complete loss of their effective power. Then their 

 antagonizing muscles induce a flexion of that limb, which is the more 

 considerable, as it is but imperfectly limited by the tendon which is situ- 

 ated at the fore part of the knee. 



The length of the os calcis, the extent of its projection beyond the in- 

 ferior extremity of the bones of the leg, tend to give firmness to the 

 erect posture, by increasing the length of the lever by which the ex- 

 tensors of the foot act on the heel, and, as, in the new-born child, this 

 bone is shorter and less projecting, the power of these muscles, whose 



port the immense vv eight of their abdominal viscera, has a considerable influence on 

 the mechanism of their motions of progression. When frif htened by any noise, they 

 spring in bounds ; and it is easy to perceive, that, at each spring", the spine becomes 

 arched and then .straightens itself, and that their motion when rapidjs effected by the 

 alternate tension and relaxation of their spinal column. JLuthvr's Note. 



