The close relation of the contraction of the brow with its early stage, a slight elevation of the eyebrows, is manifest in the fact that it occurs under embarrassment--not very regularly but almost always upon the perception of something foreign and inexplicable, or upon getting twisted in one’s talk; in fact, upon all such conditions which require greater physical and psychical clearness of vision, and hence the shutting out of superfluous light. The expression may be important on the face of a defendant who asserts,--e.g.--that he does not understand an argument intended to prove his guilt. If he is guilty he obviously knows what happened in the commission of the crime and thereby the argument which reproduces it, and even if he assures the court a hundred times that he does not understand it, he is either trying to show himself innocent or wants to gain time for his answer. If he is innocent it may be that he really does not understand the argument because he is unaware of the actual situation. Hence he will frown and listen attentively at the very beginning of the argument. The guilty person perhaps also aims to appear enormously attentive, but he does not contract his brow, because he does not need to sharpen his glance; he knows the facts accurately enough without it. It is important for the penologist to know whether a man has in the course of his life undergone much anxiety and trouble, or whether he has lived through it carelessly. Concerning these matters Darwin points out that when the inner ends of the eyebrows are raised certain muscles have to be contracted (i.e. the circular ones which contract the eyebrows and the pyramidal muscle of the nose, which serve both to pull down and contract the eyelids). The contraction is accomplished through the vigorous drawing together of the central bundle of muscles at the brow. These muscles, by contracting, raise the inner ends of the brow, and since the muscles which contract the eyebrows bring them together at the same time, their inner ends are folded in great lumpy creases. In this way short oblique, and short perpendicular furrows are made. Now this, few people can do without practice; many can never perform it voluntarily, and it is more frequent among women and children than among men. It is important to note that it is always a sign of spiritual pain, not physical. And curiously enough it is as a rule related with drawing down the corners of the mouth.