The action of the muscles and the movements resulting from it, have, on the contrary, a special character, whether taken as a whole or individually, in certain muscles of the face. In making an effort, these movements embrace the whole muscular system, and the expression which results is more characteristic. When reproduced by the plastic arts, it strongly impresses the spectator, who feels a sort of sympathetic contraction, but which soon fatigues and irritates like all inconstant attitudes.
The muscles of the face by their single or combined contraction cause the most widely differing expressions, and correspond to all the sentiments, whether simple or complex. Thus, the muscle of the forehead raises the brow in attention, admiration, or astonishment; that of the eyebrow contracts it with pain; the great zygomatic raises the angle of the lips in laughing; the triangular muscle of the lips draws them downward in weeping; other muscles co-operate in expressing combativeness, fear, anger, irony, etc, in short, the slightest phase of feeling is reproduced in the features, by the slight or energetic contractions of the muscles, which carry with them the skin to which they are intimately united, wrinkling or distending it. An eminent physiologist, M. Duchenne of Boulogne, particularized the action of these muscles in expressive movements. But though some of them may play a distinct part in the mimicry of the face, others always join in the movements when the sentiment or sensation acquires a certain vivacity; thus the muscle of the eyebrow alone may express a certain degree of suffering, but when it becomes intense the eyelids close, the nostrils dilate, and other signs beside prove the simultaneous action of the different muscles. For the physiologist and the physician, rigorously exact facts of this sort have the greatest value; but they are of less consequence to the artist, who must represent not only the muscle but the whole of the parts, near or distant, to which its action extends. If it is necessary for him to understand anatomy and the function of the muscles in order to reproduce exactly their projection during movements of the body and limbs, it is much more the study of the living model which guides him when endeavouring to render the expression of the features; and if he fails in this, it is less from ignorance of anatomy than from lack of sentiment or incapacity.
It is remarkable also how much opinion varies in regard to works of art. Each individual brings to their examination the predisposition of his studies; and if the naturalist may sometimes criticize justly, sometimes also in his judgments the artistic sentiment is replaced by the rigorous formulas and exact notions of science; he does not consider that the artist should avoid being as exact as a Chinese copy, and that a profound artistic sentiment should be completed in its expression by its counterpart in the spectator. And lastly, a savant may be a man of genius, and still lack all artistic sentiment Gratiolet, that fine and noble mind, could see nothing in Raphael's "Creation" but a "deplorable work—a furious old man striving with feet and hands to separate two thick clouds." The man who criticized one of the most admirable master-pieces of art in these terms, was a scholar of the first order, a great physiologist, and has left a work on physiognomy itself marked by the most delicate perceptions and the most profound study.