Plates 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29

(Compare each of the sides of Plates 19, 21, 22, 24, 27, and 28 while covering the opposite side.)

Plate 19: A study, as in Plate 20, of both the fundamental and secondary expressive lines produced by the moderate electrical contraction of m. corrugator supercilii, in an old man (also shown in Plates 3, 6, 7, 8, 9, 12, 13, 14, 17, and 18).

On the right, the electrical contraction of m. corrugator supercilii to a moderate degree: suffering.

On the left, the face is relaxed, with a lost look (the subject was in this state at the time of the experiment).

Plate 20: Electrical stimulation, to a moderate degree, of m. corrugator supercilii: profound suffering, with resignation. (The face was relaxed at the time of the experiment, as in the preceding figure, but the face has been illuminated in such a way as to throw a strong shadow across its lower half.)

Plate 21: Showing the antagonism between m. corrugator supercilii and m. frontalis in the same individual.

(At the time of the experiment the gaze of the subject was directed upward and his forehead was furrowed across its whole breadth, as seen in the left side of this figure.) […]