Sign language is an organized system of gestures and pantomime generally used in place of spoken words among persons lacking a common spoken language or among persons physically incapable of speech or hearing. One of the best-known sign languages is that developed by the Plains Indians of North America as a means of intertribal communication. In many respects it forms a manual counterpart to the Indian pictograph system of graphic signs painted on buckskin or birch bark. The manual signs describe things in nature, ideas, emotions, and sensations. For example, white man is indicated by drawing the fingers across the forehead, typifying the wearing of a hat; special signs exist also for Indian, for each Indian tribe, and for particular rivers, mountains, and other natural features of the physical world. The sensation of cold is indicated by a shivering motion of the hands in front of the body; by extensión the same sign is used for winter and also for year, because the Indians count years in terms of winters. A slow turning of the hand relaxed at the wrist indícates vacillation, doubt, or possibility; a modification of this sign, with quicker movement, is the question sign. Strong and strength are indicated by the motion of breaking a stout stick; bad, by a motion of contemptuously throwing something away. Song and singing are indicated by a circling movement of the fingers close to the side of the head, to indícate the shaking of the rattle which is usually used to accompany Indian Hand formation of letters used in the conversational sign language of deaf mutes
songs. As the song and rattle are used in religious ceremonials and in medical conjurations, the same sign may also mean sacred, religion, doctor, or medicine, according to the context. The signs follow the regular order of the words in the Indian sentence, and the system is so elaborate that a detailed conversation is possible by means of gestures alone. Organized sign language occurs in many parts of the world besides North America, notably among various tribes of Assam and of Australia.
Systems of manual gesture employed by deaf and dumb persons generally comprise two types of signs: natural signs, which stand for ideas or objects, and are similar to the signs discussed above; and methodical or systematic signs, which are used for word-by-word or letter-by-letter renderings of the written rather than the spoken language.
