PREFACE 



The rapid progress in the antituberculosis movement throughout 

 the world in the last five years has made it necessary to make some 

 changes in the present essay as originally presented to the Smith- 

 sonian Institution in 1908. Much that then seemed novel appears 

 almost commonplace now. An extraordinary amount of research 

 has been carried out with reference to the atmospheric air during 

 these later years. The whole theory of ventilation has been stated 

 in new terms; the presence of ozone in the atmosphere, a subject 

 that has always appealed to the popular fancy since its discovery, 

 has been restudied and its physiologic action assigned a value differ- 

 ent from that commonly ascribed to it ; the properties of strong 

 sunlight and Alpine air have been marshalled for the combat with 

 surgical tuberculosis, particularly in children. 



Physiologists in Europe and America have lately made most in- 

 teresting studies. of the blood at the higher altitudes and their obser- 

 vations are constantly throwing new light on the entire subject of 

 aerotherapy, replacing old impressions and beliefs with a scientific 

 basis on which we may confidently build. 



There never was a time when the outdoor life and the accessories 

 for the atmospheric treatment of all tuberculous persons were so 

 well systematized and placed in harmony with the other hygienic 

 measures adopted for their cure. 



What the result has been we have endeavored to show and what 

 the future holds for us we are eagerly awaiting. 



May the Smithsonian Institution, through its Hodgkins Fund, 

 continue to stimulate inquiry and disseminate the fruits of the 

 worldwide efiforts to the better understanding of the great problems 

 that yet remain unsolved. 



Guy Hinsdale. 



Hot Springs, Va., December, 1913. ' 



