The muscle of attention (left); Eyebrow contraction due to bright light (right), plate 10 from the album, The Mechanism of Human Facial Expression. Dated: 1854-1856. Dimensions: image: 22.1 ? 16.7 cm (8 11/16 ? 6 9/16 in.) mount: 40.3 ? 27.7 cm (15 7