.345 



occiput than the chin, and not corresponding* to its centre of gravity, its 

 own weight is sufficient to make it fall on the upper part of the chest. It 

 is the more disposed to fall forward, from its greater bulk, and, as in a 

 new born child the head is much larger in proportion than the other parts 

 of the body, and as its extensor muscles partake of the greater weakness 

 of that set of muscles, it falls on the fore part of the chest, and its fall 

 draws the body after it. The weight of the thoracic and abdominal vis- 

 cera tends to produce the same effect. 



Growth always proceeds from the upper to the lower parts, and this 

 law, which operates uniformly, completely eludes every kind of mechani- 

 cal explanation. It is otherwise, with regard to the effects which result 

 from this unequal growth in respect to the erect posture. The inferior 

 limbs, which serve as a base to the whole edifice being imperfectly 

 evolved at the period of birth, the upper parts placed on these unsteady 

 foundations must necessarily fall and bring them down with them. 



The relative weight of the head, of the thoracic and abdominal viscera, 

 tends, therefore, to bring forwards the line in the direction of which all 

 the parts of the body press on the plane which supports it, and this line 

 should be exactly perpendicular to that plane to enable the body to be 

 perfectly erect: the following fact proves this assertion: I have observed, 

 that children, whose head is very large, whose belly projects, and Whose 

 viscera are loaded with fat, have much difficulty in learning to stand; it 

 is only about the end of their second year, that they dare trust to their 

 own strength, and then they meet with frequent falls, and have a con- 

 tinual tendency to go on all fours. 



The vertebral column, in the child, does not describe, as in the adult, 

 three curves alternately placed, in opposite directions. It is almost 

 straight, and yet presents in the direction of its length a slight curvature, 

 the concavity of which looks forwards. This incurvation, which depends 

 solely on the flexion of the trunk while ; ri the womb, is accordingly more 

 marked, the nearer the child is to the time of its birth. 



It is well known that the curvatures, in opposite directions to the ver- 

 tebral column, add to the firmness of the erect posture, by increasing the 

 extent of the space within which the centre of gravity may move, without 

 being carried Jbeyond its limits. With regard to that use, the vertebral 

 column may be considered, as defined by two lines drawn from the ante- 

 rior and posterior part of the first cervical vertebra, to the sacro lum- 

 bar symphysis. These two lines, very near to each other at their upper 

 part, and, below, at a distance from each other, would be the chords of 

 arcs and the tangents of the curves, formed by the vertebral column. 

 So that this column may be considered as having a fictitious thickness 

 greatly exceeding its real bulk. 



In the new-born child, the want of alternate curvatures not only con- 

 tracts the boundaries within which the centre of gravity may be varied, 

 but the direction of the only curvature which exists favours the flexion 

 of the trunk, and consequently the inclination forward of the centre of 

 gravity, and the tendency to fall in that direction. This inflexion of the 

 vertebral column in the foetus and in the young child, resembles that ob- 

 served in several quadrupeds*. 



* This curvature is very distinctly marked in swine. The back of these animals is 

 remarkably prominent, and this form, necessary to enable the vertebral column to sup- 



2X ' 



