76 ELEMENTS OF PHYSIOLOGY 



126. Deformities of the Spinal Column come chiefly on 

 account of the yielding nature of the cartilage. The ex- 

 tent of the compressibility of cartilage may be realized if 

 one's height is measured upon rising in the morning and 

 again at night, when the loss in height sometimes amounts 

 to nearly half an inch. The cartilages between the verte- 

 brae are very thick, so as to give flexibility to the spinal 

 column. This blessing also brings with it a danger of 

 deformity. If the head is bent forward continuously in 

 study or work instead of being held up (Fig. 71), the 



upper cartilages are compressed in 



front, the ligaments stretch, and a 



f deformity of the neck may result, caus- 



ing the head to project forward. 

 Working with the desk low in front, 

 or working upon the ground, may 

 cause round shoulders. 



127. Tight clothing deforms the 

 ribs, which are readily movable be- 



Writing at a desk that is too r , , ., .-p.. 



high causes one shoulder cause of the long cartilages. The 

 binding down of the front ends of 

 the ribs causes posterior curvature of 

 the spine, with flat chest and round shoulders. Lateral, 

 or sidewise, curvature of the spine is caused by constantly 

 carrying the book, satchel, or other weight in the same 

 hand ; by overindulgence in the valuable habit of horse- 

 back riding (in the case of ladies) ; by writing at a desk 

 that is too high (Fig. 72); by hanging the head to one 

 side. 



128. Posterior curvature is caused by habitually bending 

 over the work, and by slipping down in the seat or desk 

 (Fig. 73). (It has been called " trying to sit upon the small 

 of the back.") It is caused also by weakness of muscles, 

 by wearing shoes with high heels, and by writing at a desk 

 that is too low. In curvature of the spine, the cartilages 



