This section is from the book "Man: A History Of The Human Body", by Arthur Keith, Sir. Also available from Amazon: Man: A History Of The Human Body.
There is a general consensus of opinion that those who pretend to read character from the shape of the head—phrenologists—and from the lines of the hand—palmists—boast of a knowledge they do not actually possess. In the course of this chapter we shall see what grounds there are for supposing that the head or hand can guide us to the character of their owner. There is one part of the body, however, we are constantly appealing to, and ever drawing inferences from—sometimes rightly, sometimes wrongly, and that is the face. Most of us believe that the face may show what the mind is really trying to hide. It is not the bony ground-work of the face that guides us, it is the expression we note. Now the skin of the face has been furnished with a special means for reflecting our mental states. It is under the control of an elaborate system of muscles, regulated by a special nerve—the facial or seventh cranial nerve. Its vessels are most delicately controlled by the sympathetic nerve system over which the will has no power. The sympathetic system responds to our emotions until experience and years have blunted the delicacy of the adjustment. In anger or in fright the vessels react to the nerve centres which control them ; they become restricted in anger, giving the face a blanched or livid appearance ; in shame or in joy the vessels dilate and our faces blush or flush. The faces of men who are exposed to all kinds of weather turn ruddy in the course of years, because the vaso-motor or vessel-regulating mechanism becomes exhausted.
As a means of expression the vaso-motor mechanism is a minor one ; the facial muscles form the chief. A pair of these muscles— the frontal—form a sheet beneath the skin of the forehead ; they can lift up the eyebrows, puckering the skin into folds which cross the brow. As long as the skin retains its youthful elasticity, and especially in those who live placid lives, free from pain or care, the wrinkles disappear as soon as the muscles cease to strain, but in most men by the age of forty, the wrinkles on the forehead have become permanent marks. The action of the frontal muscles can be reversed. If the skin of the eyebrows is fixed by bringing into action the muscle which encircles each orbit, the frontal muscles then exert their power on the scalp and move it forward. Another pair—the occipital—are attached to the scalp behind and act as opponents in moving the scalp back. Many people lose, or never acquire, the power of voluntarily throwing these muscles into action. The muscles of the scalp are especially well developed in apes, and every one must have noted how freely these animals can use them as a means of threatening their foes or welcoming their friends.
The eyes are full of expression and yet as the portrait painter knows well—it is difficult to analyse the various points on which we form our judgment. In some, the eyes seem large, in others small, but the difference is really due to the amount exposed by the lids, for as regards actual size our eyes are the least variable structures of our body. The upper lid is the real movable curtain of the eye. A special muscle within the orbit lifts it up and keeps it up so long as we are awake; in sleep it passes out of action. In alert men this muscle is strenuously in action. The upper eyelid is also provided with an involuntary muscle, which, like the arteries of the face, is regulated by the sympathetic system and alters the lid with each change in the emotional state. In fright our eyes seem to start from our heads, so vigorously do these involuntary muscles act. Soon after adult life is reached the eyelids lose their delicate outlines and the skin round the orbits becomes wrinkled and often loose. The wrinkling is due to the orbital muscle which forms a loop-shaped sheet of muscle round each orbit. The muscle is primarily for closing the lids and protecting the eyes ; we feel it come into action when we pass from the shade into the strong sunlight. It draws the eyebrows over the eyes and thus shades them. It will be observed that the skin on the cheek and temple, and on the outer side of the eyes is thrown into radiating folds or wrinkles when the orbital muscles are in action. As the skin loses its elasticity these wrinkles become permanent and form " crow's feet."
As a means of expression the muscles of the nose are not of importance. On the wing of the nose are found very reduced representatives of those strong and active muscles which dilate and close the nostrils of the winded horse. We speak of " turning our noses up " ; we have no muscles specially provided for this purpose—but there is on each side a muscle with the unsatisfactory name of compressor nasi, which has the power of drawing the adjacent skin towards the ridge of the nose— a means of expressing contempt.
The most elaborate mechanism for expression is found in connexion with the lips and mouth. The lips are used in speech and change with every form of emotion. As one may guess from the manifold movements of the lips, the arrangement of the muscles within them—the orbicular musculature of the mouth—is most complex. Special muscles are provided for lifting the upper lip and depressing the lower ; each angle of the mouth has its " levator " and its " depressor." In some, the levator is the dominating muscle and the corners of the mouth are drawn upwards into a suggested smile, just as in others the corners droop under the influence of the depressor muscles. While the skin is loosely attached on the face and cheeks, over the lips and in their neighbourhood it is closely bound down. The line Which marks the junction of the fixed labial skin with the free skin of the cheeks corresponds to a furrow which passes obliquely downwards from each side of the nose until it passes beyond and outside the angles of the mouth, thus separating the upper lip from the cheek. These naso-labial folds often deepen with age, becoming very marked in some people. They are caused by the muscles which act on the upper lip ; in laughing, for instance, the curtain-like upper lip is drawn, partly beneath the skin of the cheeks along the lines of the right and left naso-labial folds. With age the lips invariably lose their sharp outlines and their elasticity; in some they become drawn and tight under the continual contraction of the orbicular muscle situated within them; in others the muscle becomes relaxed and the mouth becomes loose and partly open or the lower lip hangs. The skin over the chin has a curious muscle which acts on it, sometimes named the " shaving" muscle, as it is employed to steady the skin of the chin against the razor. Its real use seems to consist in removing food from the recess behind the lower lip. The muscles of the cheek—the buccinator muscles—so called because they are seen in action in the puffed-out cheeks of the trumpeter, are also used in mastication, to place the food between the chewing crowns of the teeth. The muscles of the lips and cheek are employed in speech as well as in expression.
 
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