'Simultaneous contrast and areal induction flicker seem two phenomena allied inasmuch as both rest on areal reciprocity. The local exaltation or depression effected by areal reciprocity in the retina may be likened to the local spinal exaltation and depression I have called attention to in the locality of severed (or conversely excited) sensory spinal roots [note: Philosoph. Transact. CLXXXIV. B. 1893.'], with local hyperæsthesia or diminished knee-jerk for criteria [Proceedings Roy. Soc. LII. p. 17. 1893.'].' (42-43)