EFFECTS OF DEPRIVATION OF OXYGEN 231 



In the substitution-test, subjects were frequently observed 

 to stare at the test-card for several seconds before they initiated 

 the recording movements, but the delay suggested muscular 

 inhibition more strongly than anything else. The increased 

 tune required for performance in the later stages of the experi- 

 ment is due largely to loss of muscular control. In several 

 cases the subject was removed from the experiment for the 

 reason that he was unable to form a letter; in other cases, because 

 he was unable to put the pencil to the paper. 



In the opinion of the writers, the test has considerable use- 

 fulness as a means of qualitative demonstration of the effects 

 of low oxygen and of drugs. In experienced hands, it might 

 be an acceptable substitute for the routine tests now employed 

 hi the classification of aviators although the detection of initial 

 and intermediate disturbances is not quite as easy as in the 

 official test. Its simplicity recommends it highly for exploratory 

 work under external or physiological conditions which produce 

 an effect of considerable magnitude in a relatively short time. 



probably had a slighter tendency toward development of diplopia under asphyxi- 

 ation than less highly selected subjects might have. 



Besides the question of individual differences is the fact that in the official 

 test the subject's responses are made to stimuli outside his control, irregular as 

 to order and time of appearance, limited as to duration, variable as to position 

 in all three planes, and having a rather wide separation. Adequacy of response 

 therefore depended on a more highly coordinated type of eye-movement .than 

 was demanded by the conditions of this experiment. 



In the experiment made directly on vision, the subjects, even in advanced 

 stages of oxygen-deprivation, had little difficulty in maintaining steady fixation 

 and accommodation through periods of three minutes. These observations being 

 made monocular! y, diplopia did not enter. 



One would suspect that the maintenance of fixation on a single stationary 

 object, or the alternation of fixation between two stationary objects in a rela- 

 tively unlimited time, is less likely to induce and to exhibit diplopia than the 

 more trying conditions of the official test. 



While we do not contend that tendencies toward impairment of accommoda- 

 tion, convergence and muscular balance were absent in the present test, we ob- 

 tained no evidence, either from the subjects' description or behavior, that these 

 factors were operative in producing the results obtained. 



