PHYSIOLOGICAL ASPECTS OF FLYING 197 



increased. With 12 to 10 per cent of oxygen in the 

 atmosphere, nervous "exaltation" appears, approach- 

 ing in many cases almost to an intoxication, so that 

 the subject has the greatest confidence in himself, 

 although in reality his mental capacity is greatly 

 affected. This " exaltation" varies in degree with dif- 

 ferent subjects, and has been studied by experiments 

 in chambers from which the air has been gradually 

 pumped out, by such tests as getting the subject to 

 add up figures, to score out n's and r's in proofs, to 

 bisect lines of definite length. For example, the 

 writer, while testing oxygen apparatus in a rare- 

 faction chamber, has frequently experienced consider- 

 able difficulty in reading correctly the meter at 

 diminished pressures approximating to 18,000 feet. 

 With a pressure equivalent to 22,000 feet, when not 

 breathing oxygen, it has been subsequently dis- 

 covered that all the notes made were practically 

 illegible, and the writer at this time has been very 

 uncomfortable and giddy. In contrast, an old sea- 

 man, R.N., was able to assist in the manipulation 

 of the apparatus without apparently showing signs of 

 incapacity or distress. 



Finally, with very small percentages of oxygen 

 there may supervene, without warning, paralysis, 

 and, possibly, death. In the famous balloon ascent 

 of Coxwell and Glaisher to 29,000 feet, Coxwell, 

 suddenly finding himself paralysed in his limbs, 

 managed to pull the rope of the safety-valve with 

 his teeth, thereby saving himself and his com- 

 panion. 



In another famous balloon ascent the aeronauts, 

 Croce-Spinelli, Sivel, and Tissandier, were all para- 

 lysed before they could breathe oxygen from the bags 

 with which they had provided themselves, although 

 they had been warned by the famous French physi- 



