The muscle of attention (left); Eyebrow contraction due to bright light (right), between 1854 and 1856

Date: between 1854 and 1856. Dimensions: image: 22.1 × 16.7 cm (8 11/16 × 6 9/16 in.); ; mount: 40.3 × 27.7 cm (15 7/8 × 10 7/8 in.). Medium: albumen print. Collection: National Gallery of Art.