Attention (left); Severity, aggression (right), plate 17 from the album, The Mechanism of Human Facial Expression. Dated: 1854-1856. Dimensions: image: 22.1 ? 15.8 cm (8 11/16 ? 6 1/4 in.) mount: 40.2 ? 27.5 cm (15 13/16 ? 10 13/16 in.). Medium: albu