NO. I AIR AND TUBERCULOSIS HINSDALE 5 



their forests and have protected them by strictly enforcing intelHgent 

 laws so that they may be forever preserved and improved. The his- 

 tory of forestry in the United States and Canada has been that of 

 ruthless, unrestrained, wholesale destruction of nearly all our 

 standing" pine, and heavier spruce. In recent years, however, we have 

 seen the establishment of Government reserves, State reserves, and 

 State laws for their protection ; the organization of the American 

 Forestry Association, the American Forest Congress, the Society 

 for the Preservation of the Adirondack Forest; the Schools of For- 

 estry at Yale, Harvard University and Mont Alto, Penna. All these 

 remedial measures have come very late, but will undoubtedly exert 

 a strong influence for good.^ 



Aside from the general beneficial influence of forests, universally 

 recognized by climatologists, these natural parks have proved the 

 means of restoring thousands of persons suffering from tuberculosis 

 and diseases of the respiratory system. 



QUALITIES OF FOREST AIR AND SOIL 



The qualities of forest air and forest soil have been studied by 

 E. Ebermayer ' who shows that, like that of the sea and mountains, 

 forest air is freer from injurious gases, dust particles, and bacteria. 

 It was shown that the vegetable components of the forest soil contain 

 less nutritive matter (albuminoid, potash, and phosphates and ni- 

 trates) for bacterial growth; that the temperature and moisture 

 conditions are less favorable; that the sour humus of the forest 

 soil is antagonistic to pathogenic bacteria; finally that, so far, no 

 pathogenic microbes have ever been found in forest soil ; hence this 

 soil may be called hygienically pure. 



The soil is protected from high winds by forest growth and under- 

 growth ; the upper soil strata are slow to dry out and wind sweeping 

 over them carries few micro-organisms into the air. As may be 

 expected, fewer microbes are found in forest air than outside their 

 limits. Serafini and Arata have proved this experimentally.' They 



' The chief forester of the United States has in 1913 under his care in 160 

 forest reservations a total of 165,000,000 acres of forest land. The present 

 Chief Forester has done excellent work in the prevention of serious forest 

 fires. 



"^ E. Ebermayer: (i) Hygienic significance of forest air and forest soil. 

 (2) Experiments regarding the significance of humus as a soil constituent; 

 and influence of forest, different soils, and soil-covers on composition of air 

 in the soil. Wollny, 1890 (Hygeia, August 15, 1891). 



* Serafini and Arata : Intorno all 'azione dei boschi sui mikro organismi 

 transportati dai venti. 



