NATURAL HISTORY. 17 



" There closely braced, 

 And neatly fitted, it compresses hard 

 The prominent and most unsightly bones, 

 And binds the shoulders flat." COWPER. 



owing to the greater proportion of fluids to that of solids ; the 

 younger the age the greater the preponderance of fluids. The human 

 embryo when first perceptible is almost wholly fluid ; solid sub- 

 stances are gradually but slowly superadded, and even after birth the 

 preponderance is strictly according to age : for in the infant the fluids 

 abound more than in the child; in the child more than in the youth ; 

 in the youth more than in the adolescent ; in the adolescent more 

 than in the adult ; and in the adult more than in the aged. 



40. The fluids are not only more abundant than the solids, but they are also more 

 important, as they afford the immediate material of the organization of the body ; 

 the medium by -which its composition and decomposition are effected. They bear 

 nourishment to every part, and by them are carried out of the system its noxious 

 and useless matter. 



41. Why is the spinal column flexible ? 



This flexibility renders the movement of the body free, 

 easy, and varied, and accommodating to the complex combination of 

 motion which may be brought into play at any moment, with the 

 rapidity of the changes of thought, and at the command of the im- 

 pulses of feeling. If the spinal column were composed of a rigid and 

 immoveable pile of bones, all the other parts of the body, to which 

 they are directly or indirectly attached, would have been rendered 

 stiff and mechanical in their movements, and would not have beer 

 able to move, save in a given direction. 



42. The degree of flexibility which the spinal column possesses, and the extei* 

 to -which, by the cultivation of it, it is sometimes actually brought, is exemplified S T 

 the positions and contortions of the posture-master and the tumbler. It is acquir*-' 

 by means of the compressible and elastic matter interposed between the seve'a 

 vertebrae. So compressible is this substance that the human body is hult'-an-ir c " 

 shorter in the evening than in the morning, having lost by the exertions of the cJi 

 so much of its stature ; yet, so elastic is this matter that the stature lost during t* * 

 ilay is regained by the repose of the night. 



43. Whij are all the bones of the body covered with a 

 Mating, termed periosteum, except the teeth? 



Had so exquisitely sensitive a motobrano as the 



