54 COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 



was found that orange, green, and purple were perceived in their true 

 colors at 90 on the nasal retina ; violet was sometimes reported as violet, 

 but usually as violetish-blue even when the maximal luminosity available 

 was employed. There seems no room for doubt, however, that had we 

 been able to brighten our violet stimulus sufficiently it, too, would have 

 been recognized at the periphery. 



It should be borne in mind that the stimuli employed in these ex- 

 periments were equated neither in white-value nor in color-value. 

 Hence our results justify no conclusion as to the relative extension of 

 the different retinal zones. (See p. 62.) 



D. DETAILED STATEMENT OF RESULTS. 



Besides the features already described, two other phenomena of 

 indirect vision were reported by all five observers. These may be 

 described as: (o) Progressive changes in the saturation and in the 

 color-tone of the sensation which results from continuous stimulation, 

 and (b) variations of saturation and of color-tone which result from 

 changed conditions of the local chromatic adaptation of the retina. 



(o) Progressive changes of saturation and of color tone which occur during the 

 continuous application of a constant stimulus. 



It was discovered during these experiments that however con- 

 stantly and continuously the peripheral stimulus be applied, the sensa- 

 tion which it arouses is neither constant nor continuous. Not only was 

 there a marked decrease in the saturation, and sometimes in the bright- 

 ness of the sensation during the progress of the stimulation, but there 

 frequently occurred a pronounced change in its color-tone as well. The 

 matter can best be described by saying that each sensation consisted of 

 a series of more or less different phases, which ran their course during 

 the process of stimulation. The detailed records which follow show 

 the characteristics of these series. In the results which are set down in 

 Tables i, 2, 3, and 4 only the first chromatic phase of each series is 

 recorded. The succeeding phases are to be described in this section. 

 The following are typical records selected more or less at random from 

 a great number, which can not, of course, be given in their entirety : 



STIMULUS R. Lantern set at 50. At the first moment of exposure RO. appeared, 

 which changed immediately to O. This was followed by Y., 

 which became yellowish, and so persisted until die end of the 

 exposure. (It is to ibe remembered that these changes appeared 

 in the presence of an unchanging abjective stimulus, and during 

 the process of stim'ulation. The duration of each series of 

 phases recorded was three seconds, i. e., was coincident with the 

 period of stimulation. The phases were so evanescent that it 

 frequently seemed impossible to make any definite statement as 

 to the duration of each. However, -the observers were asked to 

 estimate the relative durations, and where they succeeded in 

 doing so, their reports are indicated by fractions set down after 



