Why should grief or anxiety cause the central fasciae alone of the frontal muscle together with those round the eyes, to contract? Here we seem to have a complex movement for the sole purpose of expressing grief; and yet it is a comparatively rare expression, and often overlooked. I believe the explanation is not so difficult as it at first appears. Dr. Duchenne gives a photograph of the young man before referred to, who, when looking upwards at a strongly illuminated surface, involuntarily contracted his grief-muscles in an exaggerated manner. I had entirely forgotten this photograph, when on a very bright day with the sun behind me, I met, whilst on horseback, a girl whose eyebrows, as she looked up at me, became extremely oblique, with the proper furrows on her forehead. I have observed the same movement under similar circumstances on several subsequent occasions. On my return home I made three of my children, without giving them any clue to my object, look as long and as attentively as they could, at the summit of a tall tree standing against an extremely bright sky. With all three, the orbicular, corrugator, and pyramidal muscles were energetically contracted, through reflex action, from the excitement of the retina, so that their eyes might be protected from the bright light. But they tried their utmost to look upwards; and now a curious struggle, with spasmodic twitchings, could be observed between the whole or only the central portion of the frontal muscle, and the several muscles which serve to lower the eyebrows and close the eyelids. The involuntary contraction of the pyramidal caused the basal part of their noses to be transversely and deeply wrinkled. In one of the three children, the whole eyebrows were momentarily raised and lowered by the alternate contraction of the whole frontal muscle and of the muscles surrounding the eyes, so that the whole breadth of the forehead was alternately wrinkled and smoothed. In the other two children the forehead became wrinkled in the middle part alone, rectangular furrows being thus produced; and the eyebrows were rendered oblique, with their inner extremities puckered and swollen,-- in the one child in a slight degree, in the other in a strongly marked manner. This difference in the obliquity of the eyebrows apparently depended on a difference in their general mobility, and in the strength of the pyramidal muscles. In both these cases the eyebrows and forehead were acted on under the influence of a strong light, in precisely the same manner, in every characteristic detail, as under the influence of grief or anxiety.
Duchenne states that the pyramidal muscle of the nose is less under the control of the will than are the other muscles round the eyes. He remarks that the young man who could so well act on his grief-muscles, as well as on most of his other facial muscles, could not contract the pyramidals.[5] This power, however, no doubt differs in different persons. The pyramidal muscle serves to draw down the skin of the forehead between the eyebrows, together with their inner extremities. The central fasciae of the frontal are the antagonists of the pyramidal; and if the action of the latter is to be specially checked, these central fasciae must be contracted. So that with persons having powerful pyramidal muscles, if there is under the influence of a bright light an unconscious desire to prevent the lowering of the eyebrows, the central fasciae of the frontal muscle must be brought into play; and their contraction, if sufficiently strong to overmaster the pyramidals, together with the contraction of the corrugator and orbicular muscles, will act in the manner just described on the eyebrows and forehead.
When children scream or cry out, they contract, as we know, the orbicular, corrugator, and pyramidal muscles, primarily for the sake of compressing their eyes, and thus protecting them from being gorged with blood, and secondarily through habit. I therefore expected to find with children, that when they endeavoured either to prevent a crying-fit from coming on, or to stop crying, they would cheek the contraction of the above-named muscles, in the same manner as when looking upwards at a bright light; and consequently that the central fasciae of the frontal muscle would often be brought into play. Accordingly, I began myself to observe children at such times, and asked others, including some medical men, to do the same. It is necessary to observe carefully, as the peculiar opposed action of these muscles is not nearly so plain in children, owing to their foreheads not easily wrinkling, as in adults. But I soon found that the grief-muscles were very frequently brought into distinct action on these occasions.