Bryn Mawr College monographs . 6/4 6/4 6/4 194-5 6/4 series in which the object is to measure the increase in lightsensitivity as a result of dark adaptation shows that just asacuity increases slowly with increase of illumination (exceptat very low illuminations) so also does it increase slowly withincrease of sensitivity to light. That is, the eye does notgain in acuity by adaptation nearly so fast as
Bryn Mawr College monographs . 6/4 6/4 6/4 194-5 6/4 series in which the object is to measure the increase in lightsensitivity as a result of dark adaptation shows that just asacuity increases slowly with increase of illumination (exceptat very low illuminations) so also does it increase slowly withincrease of sensitivity to light. That is, the eye does notgain in acuity by adaptation nearly so fast as it gains in lightsensitivity. In Fig. 2 the actual amounts of illumination required justto discriminate the test-object are plotted against time of A STUDY OF OCULAR FUNCTIONS 353 adaptation. It thus affords a comparison of the position ofthe minima of the different observers in the illumination scaleand comprehends data from which the following points canbe determined: (a) their relative ranking with regard to Meter-candles. 10 IS ao ft5 30 jy 40 ^-i MinutesFig. 2. Curves showing the decrease in the amount of light required just to dis-criminate the test-object as the result of dark adaptation. Inforder to standardize theinitial sensitivity, the eye was preadapted in each case for 20 minutes to 8o foot-candles of illumination (vertical component). scotopic acuity before and after adaptation, rated on the illu-mination scale; (b) their light sensitivity before and afteradaptation insofar as it affects the minimum amounts of lightrequired to discriminate the test object; and (c) their relativeamounts of change in sensitivity, measured in terms of effect 354 C. E. FERREE, G. RAND AND D. BUCKLEY on acuity, read on the illumination scale, due to of these features are important for vocational and clinicclassification. In order to make these results more directlycomparable with reference to the last of these points, namely Percentage
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