THE PHYSIOLOGY OF THE AVIATOR 97 



were undertaken by the American Air Service on the 

 enormous scale that they were. It was for the purpose of 

 testing our airmen initially, and of keeping tab on their 

 physical condition thereafter, that the work at the Mineola 

 laboratory, of which probably you have heard, was under- 

 taken. 



It is work which lies in a field of physiology in which 

 before the war not half a dozen men in America, and not 

 many more in Europe, were interested, and for them it 

 was a field of what is called "pure" science. To-day it 

 promises contributions of practical value not only to 

 aviation, but to problems in medicine, climatology, ath- 

 letics and hygiene. 



We will turn then to the problem of the aviator and 

 the methods of human engineering which have been de- 

 veloped for its solution. But first, it will be advisable to 

 review briefly what is known concerning the immediate 

 effects of low barometric pressure and the functional re- 

 adjustments involved in acclimatization to elevated re- 

 gions; that is, life at great altitudes. 



Paul Bert, 1 the brilliant French physiologist, was the 

 first to demonstrate, in 1878, that the effects of lowered 

 barometric pressure or altitude are wholly dependent on 

 the decreased pressure of oxygen. He carried out experi- 

 ments upon men and animals both with artificial gas mix- 

 tures and reduced barometric pressure in a steel chamber. 



He showed that in pure oxygen at 21 per cent, of at- 

 mospheric pressure life goes on in practically the same 

 manner as in air, which contains 21 per cent, of oxygen, 

 at the ordinary pressure. So also the breathing of an 

 artificial gas mixture containing only 10.5 per cent, of 

 oxygen has the same untoward effects at sea level that 

 breathing pure air has at an altitude of about 20,000 feet, 

 where the barometer is reduced by one half. 



These considerations are fundamental for the differen- 

 tiation of the disorders induced by rarefied air so-called 



1 Paul Bert, La Pression Barometrique, Paris, 1878. 



