great leaders of commerce and public life. On the other 

 hand, collapsed positions are characteristic of both physical 

 and mental weakness. They constitute a distinct aspect 

 of weakness and illness, from the tuberculosis patient to 

 the feeble-minded." * 



In sitting, the body should be bent only at knees and 

 hips, and the head, neck, and trunk should be kept in one 

 straight line. 



Another important element in hygiene is the exercise of 

 the organs of breathing. In ordinary breath- _ 



ing only about ten per cent, of the lung R . . 



contents is changed at each breath, and the 

 remoter air sacs of the lungs which are not properly exer- 

 cised are peculiarly liable to disease. The high mortality 

 from tuberculosis among clerks, bookkeepers, telegraphers 

 and other indoor workers whose tasks require or invite a 

 stooping posture are examples of such harmful effects. 

 "A hundred deep breaths a day" is one physician's recipe 

 for tuberculosis, according to Fisher and Fisk. Deep 

 breathing should be slow and not forced. 



FRESH AIR 



Variations in the chemical composition of the air are of 



little practical moment, except for the pres- „„ „ « A . 

 r r j j j Why Bad Air 



ence of poisonous fumes and dust under T tt c i 



special industrial conditions. Even in the 

 worst ventilated room the proportions of carbon dioxid and 

 oxygen never change sufficiently to produce harmful physi- 

 ological effects. The discomfort and injury to health that 

 come from living in badly ventilated rooms are due not 

 primarily to any chemical changes but to the rise in tem- 

 perature that obtains under such conditions. 



This does not mean that fresh air is unimportant, but 

 quite the contrary. A badly ventilated room is generally 

 * Jessie H. Bancroft, in The Teaching of Hygiene. 

 17 



