Cited by C.S. Sherrington, 'On Binocular Flicker and the Correlations of Activity of 'Corresponding' Retinal Points', Journal of Psychology 1 (1) (1904), pp. 26-60.
Description:

'Exner and Charpentier have pointed out that the peripheral retina is more sensitive to flicker than the central, and Exner has shown that an area only 1330µ from the fovea is more sensitive in this respect than the fovea itself. In the observations now in consideration the flicjker sensitivity of points only 750µ from the foveal centre was found perceptibly greater than that of the foveal centre itself.' (33)

Cited by C.S. Sherrington, 'On Reciprocal Action in the Retina as studied by means of some Rotating Discs', Journal of Physiology 21 (1) (1897), pp. 33-54.
Description:

'Fick [note: 'Arch. f. Anat. u. Physiol. 1863.'] has shown that a more intense light sensation developes more speedily than does a less intense. Exner's [note: 'Sitzungsb. d. k. Akad. d. Wiss. Wien, 1868. Pflüger's Archiv, III. p. 214. 1870.'] actual measurements found the time decrease nearly arithmetically with geometrical increase of luminosity of stimulus.' (35)

Cited by O.F.F. Grünbaum, 'On Intermittent Stimulation of the Retina (Part II)', Journal of Physiology 22 (6) (1898), pp. 433-450
Description:

'Two main theories have been suggested to explain the fact that intermittent retinal stimuli repeated above a certain frequency give rise to a steady sensation.

The older, which I shall in future style the "persistence theory," seems to have been suggested by d'Arcy [note: 'Mem. Akd. Sci. p. 439. 1765.'] in 1765 and maintains that a steady sensation results from intermittent stimuli, when the intervening periods do not exceed the time of duration of the positive after-image of undiminished brightness: in fact, attempts were made by this observer to determine this quantity by noting the minimum freouency with which a burning coal must be rotated in order to produce a sensation of a ring of fire: 0.133 secs. was his estimation.

All subsequent writers, Plateau, Talbot, Helmholtz, etc. adopt d'Arcy's view, Fick [note: Hernann's Handbuch, III. p. 215. 1879.'] being the first to suggest an alternative. This author accepted Exner's [note: Sitzungsberichte Akad. Wein. LVIII. p. 601. 1868, and Pflüger's Archiv, III. p. 240. 1870.'] conclusion, that if the eye be exposed to black after having been stimulated by light, there is at first a rapid fall in the brightiness of the positive after-image, which then more gradually disappears; the curve representing the decrease and disappearance being of exactly a similar nature to that representing the growth of sensation produced by a white stimulus.

Fick diagrammatically represented the sensation resulting from intermittent stimulus by a serrated line, the abscissa being the timerelation and the ordinates the strength of sensation, and pointed out that if the frequency become great, the amplitude of oscillation of sensation diminishes until a frequency is reached at which a continuous smooth sensation results.

It is surprising that writers after Fick's explanation did not adopt his view, since even if Exner's statement that under normal conditions the duration of the after-image of undiminished brightness is infinitely short, be disallowed, nevertheless the persistence-theory seems unsatisfactory' (443-444)