HEAT IN RELATION TO THE HUMAN BODY 



21 



air in some cases is made to pass through a room where in 

 some one of various ways it is " washed" free of dust and 

 other impurities, and given the desired amount of moisture. 

 In winter it may then be warmed by passing it over steam 

 coils before distribution in the building, and in summer it 

 may be cooled by use of ice. Continuous stirring of air 

 that is not changed in any other way has been found to afford 

 marked relief in ill-ventilated rooms. The movement of the 



FIG. 8. Framework of the chest walls. In B the chest cavity has been 

 enlarged by the contraction of the rrmscular walls; and in A decreased by the 

 relaxation of these same muscles. 



air lessens the discomfort and sense of depression occasioned 

 by having warm moisture-laden air remain stagnant around 

 a person. 



Serving as a partition between the chest and abdominal 

 cavities the diaphragm (di'-a-fram) is attached at its circum- 

 ference to the side walls of the chest. The framework of the 

 chest is made up of the ribs, the spine, and the breast-bone. 

 The muscular fibres of the diaphragm are so arranged that 

 it is flattened downward when they contract, thus crowding 

 the stomach, liver, and intestines outward and enlarging the 

 chest cavity. Not least among the beneficial effects of deep 



