J.E. Purkynĕ's contributions to the physiology of the visual, the vestibular and the oculomotor systems.

J.E. Purkynĕ (1787-1869) was one of the leading physiologists in the first half of the 19th century, became the founder of the "exact subjectivism", and remained during his entire life a very careful observer in psychophysical experiments. He made moreover many important discoveries in anatomy, neuroanatomy, embryology and pharmacology. Despite his outstanding contributions to science, he remained in his general philosophy and feelings deeply attached to the Romantic spirit of the age. After Purkynĕ returned to Prague in 1849 he played an important role in his nation's search for a national identity and became a leading figure in the cultural and social life of Prague. Purkynĕ's contributions to the physiology of vision, the oculomotor and the vestibular systems are reviewed. In vision Purkynĕ discovered the Purkynĕ-tree, flicker patterns seen in diffuse light, moving light nebula in the Eigengrau, spatially patterned structures in pressure phosphenes, the antagonistic properties of Galvanic phosphenes with respect to current polarity, periodic afterimages, the Troxler effect for colour perception with the peripheral retina and the principle of the ophthalmoscope. The Purkynĕ-shift in chromatic sensitivity when the adaptation level shifts from scotopic to photopic vision was rediscovered by Purkynĕ. Purkynĕ was the first to describe the "Purkynĕ images" of the anterior and posterior surfaces of the cornea and the lens and the changes in the third Purkynĕ image when the eye accommodates. He described optokinetic nystagmus and optokinetic after-nystagmus and explained movement aftereffects as a habituation of the gaze motor system. Important contributions were made by Purkynĕ to the physiology of the vestibular system, but he did not propose the existence of peripheral receptors for this system. He believed that direct mechanical effects on certain parts of the brain (especially the cerebellum) are responsible for the mechanisms of vertigo. Purkynĕ's five categories of vertigo are still valid today (vertigo of motion, Galvanic vertigo, vertigo caused by general brain ischemia, height vertigo and vertigo caused by alcohol and other narcotics). Purkynĕ's contribution to sensory physiology can be considered as one of the essential foundations on which modern sensory physiology and psychophysics are built.