BREATHING 



175 



237. The Dangers from Pulmonary Infection. There is 

 an infectious disease called tuberculosis of the lungs, but com- 

 monly known as consumption. It is caused by the growth 

 within the lungs of a disease germ called bacillus tuberculosis. 



The sputum of a 

 consumptive swarms 

 with these bacteria. 

 This infected matter, 

 falling upon the street 

 or about a room, soon 

 dries and may become 

 mixed with the com- 

 mon dust floating 

 through the air. It 

 may retain its vitality 

 for a long time as a 

 part of the dust of 

 damp, filthy, or over- 

 crowded houses. 



. A minute portion of sputum from a case of phthisis, 



1 niS ClUSt When in- or consumption of the lungs, magnified 1000 diam- 

 eters. These bacilli are rod-shaped bacteria, 

 stained to show black. The black spots in the 

 figure are merely the debris in the sputum, also 

 stained so that they look black. 



FIG. in. Bacillus Tuberculosis. 



haled often finds in 

 the body a congenial 

 soil upon which the 

 seeds of this dread disease may be transplanted. 



238. Ventilation. The best way to rid our rooms and 

 premises of impure air is by some suitable system of venti- 

 lation, that is, some practical and efficient plan to keep 

 the air pure and wholesome without making it too cold. If 

 we do our best, however, we cannot keep the air of our living 

 rooms as pure as the outside air ; for, as we have seen, 

 every person in the room, with every breath, is consuming 

 the oxygen and imparting carbon dioxide to the air. 



