Page:Popular Science Monthly Volume 45.djvu/396

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ALTHOUGH from infancy upward we are all, whether we know it or not, close students of physiognomy, and although a number of books, the result of much careful research, have been published upon the scientific aspect of the subject, there are certain facts connected with facial expression which, though often remarked upon, have never received explanation. With two of these-both of which bear upon the causes of acquired expression of a more or less permanent character—I propose briefly to deal in this article. I refer to the similarity of visage displayed by nearly all members of certain trades and professions; and to the likeness which often becomes apparent on the faces of people (generally married couples) who live together.

In addition to the bony framework, there are three chief anatomical factors which go to make up the expression of the face. These are the skin, the subcutaneous cushion of fat which contains the numerous blood-vessels, and, lastly, the facial muscles. The nerve supply is abundant and peculiar. The integument receives sensory branches from the fifth cranial nerve, the blood-vessels are under the control of the sympathetic system, and the muscles which have to do with expression receive motor impulses from the brain via the seventh cranial or facial nerve, first accurately described by Sir Charles Bell. It is to these numerous slips of muscular tissue, with their controlling telegraphic nerve fibers, that I wish especially to direct attention.

It is, of course, obvious to all who have an elementary knowledge of physiology that any movement of any part of the face is owing to the contraction of certain muscles, and that every such contraction must take place at the command of an impulse conveyed to the muscles by means of the motor nerves.

Into the historical evolutionary explanation of these movements it is not my intention here to enter. Let it suffice to say that there can be little doubt that they one and all represent some adaptation of the bodily structures to certain physical needs (possibly long obsolete) which accompanied the emotions of which the movements are now an index; just as the wagging of a dog's tail, which is now regarded as a mere sign of pleasurable excitement, was in the first place of vital importance as a signal to his comrades that game was afoot.

The connection between the muscles of expression and the emotional centers in the brain is of a most intimate character, and is largely independent of the will, although by strong volition any consequent movement of the features may generally be pre-