Four Dancers

Four Dancers, Edgar Degas, 1899 Breezing Up, Winslow Homer, 1876 Persistence of Memory, Salvador Dali, 1931 The Starry Night, Vincent van Gogh, 1889... 

In a disease control experiment in 1979 (H. Cole, unpublished), triadimefon was applied to four wheat varieties ( Red Coat, Hart, S-76, and Dancer ) grown under both a high fertility regime... 

Imagine a dancer who at different times has various combinations of hands and feet raised. The relationship between right hand-right foot raised and left hand-left foot raised is a mirror-image, enantiomeric one. Neither is the mirror image of, say, right hand-left foot raised, so the latter is diastereomerically related to the first two. The illustration below shows how the four possible combinations of one hand up, one hand down, one foot up, one foot down are related in a way similar to the four stereoisomers of a molecule with two chiral carbons. 

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