244 



PHYSIOLOGY AND HEALTH. 



be supported from the knees and the legs by the feet resting 

 upon the floor. Too many of the school-rooms are furnished 

 with seats built upon one uniform model and of the same 

 height. If these are high enough for the older and larger 

 children, they are too high for the younger and smaller. 

 When, therefore, these sit, the lower leg and foot hang from 

 the lower part of the thigh, which projects beyond the seat, 

 and may cause it to suffer. (Fig. XXX.) The weak bones 



FIG. XXIX. 



FIG. XXX. 



of this age do not well bear long continuance of any posture ; 

 the attitudes, therefore, should be very frequently varied. 



591. This process of consolidating the bones from infancy 

 to old age is gradual, and is one of the evidences of good 

 health. But in some feeble persons the lime is not deposited 

 in the usual proportion, and the gelatine prevails through life, 

 as in childhood ; this is the disease familiarly known as the 

 rickets. The bones are then weak, and liable to be bent. 

 The heads of such bones are generally enlarged and 'misshapen, 

 and the shafts frequently crooked. The spine is curved, and 

 sometimes the skull is enlarged. This disease happens mostly 

 among those who are badly nourished, who have poor and 

 insufficient food, who live in damp and dark rooms or hovels, 

 and breathe foul air. 



592. The bones are not solid. Their inner parts are loose 



