230 H. M. JOHNSON AND FRANKLIN C. PASCHAL 



INTERPRETATION OF RESULTS 



The assertion has been made 4 that in some early experiments 

 with this type of test, the performance seemed to be modified 

 to an important extent by disturbances of accommodation and 

 of oculomotor adjustment. 



We were not successful, in the work reported in this paper, in 

 obtaining evidence hi support of this view. A supplementary 

 experiment was made by Capt. Johnson, for the purpose of 

 measuring disturbances of vision due to these factors. The 

 results are not yet ready for publication, but are entirely negative. 

 The characteristics of the records obtained indicate that the 

 disturbances were more probably attentional than sensory. A 

 similar uncertainty exists regarding all the rest of the work done 

 directly on sensory process as affected by low oxygen. 



One of the present authors has repeatedly reacted in experi- 

 ments on the effects of oxygen-deprivation, and has noted that 

 as collapse approaches, there is a great depression of vision; but 

 it is manifested, not in the blurring of outlines of objects, but 

 in a general darkening of the visual field and an intermittent 

 cessation of all visual experiences (including that of darkness) 

 together. This is especially marked in tests in which pure nitro- 

 gen is breathed instead of air, as the effect occurs very quickly 

 and is clearly noticed; and the duration of the test being very 

 short, the effect is more readily appraised afterwards than hi 

 the case of longer experiments. The other author has reacted 

 hi fewer experiments but his experience is very similar. A 

 number of other subjects report a similar observation; and records 

 made in a continuous, self-recording, test of visual acuity show 

 the same tendency. 6 



4 Manual of Medical Research Laboratory; Washington, Government Print- 

 ing Office, 1918; p. 181. Also: Air Service Medical; Washington, Government 

 Printing Office, 1918; p. 311. 



6 The authors do not regard this evidence as conflicting with the early diplopia 

 reported by Dunlap as having been observed on himself and other subjects. 

 (Cf. reference cited in footnote 1, above.) Dunlap's observation has received 

 ample corroboration under the conditions under which it was made. 



In the work reported in this paper, all the subjects were free from phorias or 

 oculomotor imbalance, or possessed these defects in negligibly small degree. They 



