Optics and Biologic Connectedness

“...I is this passion for beautiful colors that makes us paint as we do... and not the love of the ‘dot,’ as foolish people say,” wrote painter Paul Signac in his journal (1). He was defending the art movement started by his good friend and fellow artist George Seurat and built upon by Signac himself, Camille Pissarro, and others. This movement, divisionism or pointillism, was Seurat’s artistic contribution during a brief but extraordinary life. Parisian from a middle-class family, tall, and handsome, Seurat enjoyed a comfortable life and proper education. He showed early talent for drawing, studied sculpture, and attended the prestigious Ecole Des Beaux-Arts. A competent photographer, he became interested in the workings of light, particularly in black-and-white images. This interest grew as he studied optics and the processes at work on the silver particles of photographic film (2). During his art studies, particularly under the tutelage of a student of Ingres, he came to believe in a systematic approach to art. Nicknamed “le notaire” (the notary) for his immaculate attention to his appearance, Seurat was temperamentally suited for a scientific approach to art (3). Idiosyncratically bent toward order and control and gifted with formidable observational skills, patience, concentration, and painstaking adherence to detail, he embarked on a style of painting based on color and structure that was cerebral and calculated. Like the impressionists, Seurat was interested in the relationship between natural light and the application of paint, only he wanted to create an impression not on the canvas but in the mind of the viewer. Influenced by the work of French chemist Michel-Eugene Chevreul (1786–1889), he believed that next to each other, colors appear as dissimilar as possible, both in optical composition and tonal value (4). Seurat’s color theory, in which the viewer plays a key role in perception, influenced the development of modern art. His artistic goal, Seurat once said, was to show “modern people, in their essential traits, move about as if on friezes, and place them on canvases organized by harmonies of color, by directions of the tones in harmony with the lines, and by the directions of the lines” (5). In his best known work, images are tightly structured as if on a grid, the figures systematically placed in relation to each other in permanent, non-negotiable arrangements. Pure color is used directly from the tube, in static “points” clearly separate but intended to merge in the viewer’s eye, producing a confluent image brighter than any achieved with brushstrokes. Like many scientific experiments, Seurat’s daring process had unexpected results. The points remained visible, akin to tesserae in a mosaic, but produced a shimmering translucent effect (5). A Sunday Afternoon on the Island of La Grande Jatte, on this month’s cover of Emerging Infectious Diseases, is Seurat’s masterpiece and one of the bestknown works of the 19th century. The placid scene in an island park on the Seine shows a local crowd during a moment of leisure outdoors. Seurat’s version of this commonplace event is revolutionary. As figures register in the viewer’s eye, they seem suspended in mid-moment, levitating yet permanently fixed. Prototypes rather than likenesses, they represent workers in shirt sleeves, fashionable couples, children at play, soldiers in uniform. Seurat did not dwell