repressed by the will, the strictly involuntary muscles retain their action, and may be highly expressive; and when, on the other hand, the will is relaxed, the voluntary muscles fail before them. Debility of the brain, Sir C. Bell remarked, is most shown in the case of those muscles which are in their natural condition most under the control of the will. A further mode of expression arises when the checking of one habitual movement calls up another.
"The second principle is that of antithesis. When certain movements or gestures have been acquired as aforesaid, and have come to be habitually performed in connection with a certain state of mind, there will then be a strange and involuntary tendency under the opposite state of mind to directly opposite movements, whether in any way serviceable or not. Hence alone, Mr. Darwin thinks, can be explained, not only the sudden and extreme changes of expression in the attitudes of animals, but many gestures used by savages, or by the deaf and dumb. This antithesis in attitude, from anger and defiance to affectionate crouching, is illustrated by him in the case of the dog and the cat, by means of photography. The Cistercian monks, among whom speaking was sinful, invented a gesture language, founded upon the principle of antithesis. It is clear that in this principle the will intervenes largely.
"Mr. Darwin is, however, less confident in referring expressive signs or gestures to the action of this principle, than to his third originating cause, the direct agency of the nervous system. When the sensorium is strongly excited, nerve-force is generated in great excess, and is transmitted in certain directions, determined by the connection of the nerve-cells, or, where the muscular system is concerned, by the nature of the movements of face or limb, which correspond to each nervous impulse. These are, at the first, at least, independent of the will, or even of habit, though in later stages habit may have considerable play, inasmuch as nerve-force tends to pass along accustomed channels. Mr. Darwin inclines to think that what seem the most strictly involuntary actions, such as the bristling of the hair in fear or anger, may have been effected by the mysterious power of the will. He is far, however, from laying down dogmatic views upon the operation of these various agencies in causing or varying expression, nor is he prepared to draw sharp lines between the action of his three elementary principles. Many phases or signs of expression may partake, he considers, of all three, and may be referable to no single or direct physiological cause. The visible apparatus of expression may of course be taken as muscular, and he begins with laying down diagrams of the various muscles of the face in man, those in particular which are connected with the eyes and mouth..... Suppose we take as an illustration the oblique or upturned eyebrows of a man suffering from grief or anxiety. Every one must be familiar, both from Nature and works of art, with the way in which the inner angle of the eye-
