PHYSIOLOGICAL ASPECTS OF FLYING 199 



been at fault. In reality the camera had been in good 

 working order, and it was he who, owing to muscu- 

 lar weakness, could not pull the shutter, or, owing to 

 his cerebral condition, forgot to change his plates. In 

 some cases hallucinations occur at such high altitudes, 

 e.g. the reporting of phantom hostile air-craft flying 

 at quite impossible heights. 



Since, however, the length of even long flights is 

 of relatively short duration, there is but little oppor- 

 tunity for any acclimatization of the body to high 

 altitudes. No airman can yet take the air and remain 

 at a height of 15,000 to 20,000 feet for the seven to 

 ten days necessary to give him any permanent degree 

 of acclimatization. 



Supposing a man is a high flier, and has been in 

 the air for 1000 hours in the course of i J to 2 years, 

 it is probable that the time he has spent above 15,000 

 feet is 240 hours (or 10 days) at the most in that 

 period. In other words, his total stay at a high 

 altitude has been so short and so intermittent that 

 there has been no time for any acclimatization to take 

 place. It is this which complicates the subject of 

 flying stress, and renders the information obtainable 

 from previous literature of but little service, thus 

 necessitating the tackling of the problem afresh. 



It must be emphasized that in regard to the so- 

 called illnesses associated with flying, one is not 

 dealing with any definite malady, such as divers' 

 palsy or caisson disease, for disabilities resulting 

 from flying are due almost solely to the wear and 

 tear on the organism as a result of repeated inter- 

 mittent strain upon the bodily mechanisms. The 

 condition of fatigue which ensues as the result of 

 flying may arise equally from other forms of stress, 

 such as severe and prolonged exposure in the trenches. 



Considerable misconception prevails as to the effects 



