A Trick of the Eye

Jan Purkinje, a histologist and physiologist whose findings led to important insights into how the body works, was born on this day in 1787. Purkinje is famous for explaining visual phenomena: the Purkinje effect describes how blue objects appear brighter than red objects in dimmer light. And Purkinje's images are the threefold reflections seen in the eye of another person, caused by an object reflecting from the cornea's surface and both sides of the lens.

Purkinje also discovered the large nerve cells with numerous dendrites in the cerebellum. He was the first to identify unusual muscle fibers in the membrane lining the heart, now known to conduct the pacemaker stimulus. He was also the first to spot the sweat glands by sight, not smell. In his spare time, Purkinje improved techniques for preparing tissue samples, using a microtome--an instrument that slices tissues into very thin samples.

[Source: Roy Porter, Ed. The Biographical Dictionary of Scientists, Second Edition. Oxford University Press. 1994.]