280 BIOLOGICAL PROBLEMS 



air" hospital conditions, and he gives evidence of 

 how much better his patients did in old drafty tents 

 than in crowded hospital wards. At the same time 

 Brocklesby, an army surgeon, furnished similar testi- 

 mony. Notwithstanding the cold and dampness of 

 old sheds in which the soldiers were placed, he states 

 that remarkably fewer died from the same disease, 

 though under the same regimen and treated in the 

 same manner, than was the case with those in hospital 

 wards, and that the convalescents recovered sooner 

 than those in the warmer and more weather-proof 

 huts. 



There is a mass of evidence to justify the conclusion 

 that a lack of fresh air exerts a markedly deteriorat- 

 ing effect upon both mental and physical powers. 

 But before indicating the nature and extent of the 

 observations and experiments which constitute this 

 evidence, it will conduce to a clearer understanding 

 of the issues if I endeavour first to explain the close 

 relationship of foul air to disease and loss of efficiency. 



The research of recent years has done much to 

 elucidate this biological problem, but the limitations 

 of time do not permit me to do more than summarize 

 this research. In this matter we have slowly felt our 

 way to a scientific objective hypotheses, based on 

 imperfect knowledge, have been framed from time to 

 time to explain the observed facts, and these have 

 been tested in the light of an improving knowledge, 

 and discarded to make place for the recent real advance 

 of our knowledge on this subject. For this advance 

 we are mainly indebted to the work, within recent 

 years, of Haldane, Fliigge, Leonard Hill, and certain 

 American experimentalists. 



The harmful effects of stuffy air were first ascribed 

 to a form of poisoning, due either to the altered 

 gaseous constituents of the air or to the presence of 



