. Medical studies in aviation . e of day andin time interval to those taken in the low-pressurechamber. At 5,000 and 10,000 feet there is usually aslight enlargement of the fields for form and color,at 15,000 a slight contraction, and at 20,000 a markedcontraction. Twenty men have been examined, and at20,000 feet the fields for form have shown a contrac-tion of 14 per cent, of their original size below, percent, in the temporal field, 4 per cent, above, and 8 percent, in the nasal field. The red has lost 9 per cent,below, per cent, temporally, 4 per cent, above, and 6per cent, nasally.
. Medical studies in aviation . e of day andin time interval to those taken in the low-pressurechamber. At 5,000 and 10,000 feet there is usually aslight enlargement of the fields for form and color,at 15,000 a slight contraction, and at 20,000 a markedcontraction. Twenty men have been examined, and at20,000 feet the fields for form have shown a contrac-tion of 14 per cent, of their original size below, percent, in the temporal field, 4 per cent, above, and 8 percent, in the nasal field. The red has lost 9 per cent,below, per cent, temporally, 4 per cent, above, and 6per cent, nasally. The green, per cent, in the lower,5 per cent, in the temporal, 5 per cent, above, and 25per cent, in the nasal field. Five minutes after return-ing to sea level, fields are normal in size. Givingoxygen at 20,000 feet for four or five minutes causes 53 a return of the field to normal. Several fields havebeen taken on the rebreathing apparatus, and theresults are fairly comparable with those found in thelow-pressure O 5 10 15 20 li 30 35 AO a JO SS 10 »J Fig. 3.—Falling off of accommodation and convergence in low-pres-sure chamber and return of strength on administration of oxygen. PERCEPTION OF MOTION AND ITS DIRECTION BYTFIE RETINA Perception of motion and its direction is of greatimportance to the aviator, and a test has been devisedin this laboratory that will give some indication ofthe fliers power in this respect. The best pilots feelthat by constant practice they may develop this impor- 54 tant function to a marked degree. The test is per-formed with the subject seated 15 inches from aBjerrum screen, fixing with both eyes a 3 mm. whitepin placed in the screen on a level with the eye. Asmall light, which is visible through the cloth orneutral gray paper is used as the test object. The pointat which the test object is first noted and where thedirection of motion in three planes is first accuratelydescribed is recorded on a chart for use with the tan-gent sc
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