CHAP. XIV. AND SUMMARY. 355 cruage used by the deaf and dumb. On the contrary., everv true or inherited movement of expression seems to have had some natural and independent origin. But \vhen once acquired, such movements may be voluntarily and consciously employed as a means of communication. 32 ven infants, if carefully attended to, find out at a very ly age that their screaming brings relief, and they voluntarily practise it. We may frequently see a person voluntarily raising his eyebrows to express sur- prise, or smiling to express pretended satisfaction and Acquiescence. A man often wishes to make certain ges- tures conspicuous or demonstrative, and will raise his extended arms with widely opened fingers above his liead, to show astonishment, or lift his shoulders to his ears, to show that he cannot or will not do something. The tendency to such movements will be strengthened or increased by their being thus voluntarily and repeat- edly performed; and the effects may be inherited. It is perhaps worth consideration whether move- ments at first used only by one or a few individuals to express a certain state of mind may not sometimes have spread to others, and ultimately have become universal, tlirough the power of conscious and unconscious imita- tion. That there exists in man a strong tendency to imitation, independently of the conscious will, is certain. TMs is exhibited in the most extraordinary manner in certain brain diseases, especially at the commencement of inflammatory softening of the brain, and has been called the " echo sign." Patients thus affected imitate, without understanding, every absurd gesture which is made, and every word which is uttered near them, even in a foreign language.1 In the case of animals, the jackal 1 See the interesting* facts given by Dr. Bateman on * Aphasia/ 1870, p. 110.