n :  a second positive afterimage in a succession of visual afterimages resulting from a brief light stimulus and appearing most distinctly in a hue complementary to that of the original sensation
 
Pur•ky•n (or  Purkinje ) Jan Evangelista (1787-1869), Bohemian physiologist. Purkyn was a pioneering physiologist who made major contributions to histology, embryology, and pharmacology and whose discoveries considerably increased our understanding of the composition of cells, the functions of the brain and the heart, mammalian reproduction, and the phenomena of human vision. His best known discoveries include the large nerve cells in the cortex of the cerebellum that are known as Purkinje cells (1837) and the fibrous tissue that conducts the pacemaker stimulus along the inside walls of the ventricles to all parts of the heart (1839); the fibers are known as Purkinje fibers and make up Purkinje's network. He wrote his graduation dissertation in 1823 on the subjective phenomena of human vision. One such phenomenon is now known as the Purkinje phenomenon.
 
 
 
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