280 § ANNUAL REPORT SMITHSONIAN INSTITUTION, 1944 
chambers, both on mountains and in aircraft, on the nature of alti- 
tude sickness and the ways of overcoming it: 
Plate 3, figure 1 shows a modern decompression chamber at an 
R. A. F. Medical Service research unit. In this a man can be taken 
to a pressure equal to that at 30,000 feet in less than a minute, and it 
is capable of producing pressures down to a small fraction of a pound 
to the square inch. 
Plate 3, figure 2 shows a small type of decompression eine of 
which many are in service, which will take six men to any altitude 
required so that they can become familiar with their breathing 
apparatus and the disasters that may befall them if they do not use 
it correctly. 
For life, man needs food, water, and air. He can live without food 
for weeks, without water for days, but without air he can survive 
only a few minutes. 
At increasing altitudes, although the proportion of oxygen in the 
air remains one-fifth, the density of the mixture becomes less and a 
certain pressure of oxygen is essential for living cells to function 
normally. At an altitude of 42,000 feet if the lungs are filled with air, 
they contain less than one-sixth of the normal quantity of oxygen and 
this is insufficient to support life. Much of the Battle of Britain was 
carried out in an atmosphere in which a pilot unassisted with breathing 
apparatus would be dead in a few minutes. However, long before this 
height is reached oxygen lack makes its presence felt in the impaired 
intelligence and mental performance of the pilot. As oxygen want 
comes on, judgment is lost, gross errors are made, intelligence fails, 
muscular control is lost and this is followed by unconsciousness. 
Moreover, oxygen want is very insidious because the sufferer is often 
almost unaware of it. At 20,000 feet a man without oxygen may do 
irrational things; oxygen want resembles drunkenness both in its 
symptoms and in that the sufferer is confident that he is normal and 
much resents any suggestion to the contrary. 
It would clearly be dangerous to send an aircraft up to 25,000 feet 
unless it was ensured that the crew were protected from oxygen want. 
Much research on the practical protection of flying personnel from the 
effects of altitude has been carried out by the R. A. F., particularly by 
the Medical Branch which directs research in this very important side 
of the pilot’s welfare. The importance of this is emphasized by the 
following story of a recent incident which occurred over Ger- 
many. A pilot’s breathing apparatus became disconnected and the 
pilot thereupon told the crew that he was going to land. He put down 
his wheels and tried to land on a cloudbank at about 18,000 feet. He 
then told the crew over his intercommunication system that they were 
below ground level and he was going to get out, whereupon the navi- 
