Donders' Law
Historical document, translated for reference. It reflects medical knowledge of the 1920s–30s and is not medical advice.
Summary
Donders' Law states that the orientation of the retina remains constant relative to external space. The law describes how the eyes move in primary, secondary, and tertiary positions, with tertiary positions causing rotational movements that do not significantly affect spatial perception due to habit.
Encyclopedia article (1928–1936)
DONDERS' LAW (Donders), the law of constant orientation of the retina relative to external space. The visual lines of both eyes always lie in one plane—the visual plane. If this plane coincides with the horizontal plane and the visual lines intersect in the sagittal plane, then this position is called primary. When the visual plane rotates around the horizontal axis (movement up-down) or vertical axis (movement right-left), the eyes move to a secondary position, in which the horizontal and vertical meridians of the retinas do not change their position. If the visual plane simultaneously rotates around both horizontal and vertical axes (e.g., right or left, down-up), then a tertiary position is obtained, in which the eyes perform wheel-like rotation around the sagittal axis, and consequently the mentioned retinal meridians rotate by a corresponding angle. Due to the slight rotation (and mainly our habit), these wheel-like movements of the eyes do not noticeably disrupt our correct assessment of spatial relationships.
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Cite this page
“Donders' Law.” Soviet Medical Encyclopedia. English translation of Bolshaya Meditsinskaya Entsiklopediya, 1st ed. (Moscow, 1928–1936), ed. N. A. Semashko. https://sovietmedicalencyclopedia.pages.dev/article/donders-law/