Wherever the buffaloes were present in large numbers, the habits of the Indians were much the same. They could not live in settled villages, for there was no assurance that the buffalo would come to any particular place each year. The plains tribes were therefore more thoroughly nomadic than almost any others, especially after the introduction of horses. Because they wandered so much, they came into contact with other tribes to an unusual degree, and much of the contact was friendly. Gradually the Indians developed a sign language by which tribes of different tongues could communicate with one another. At first these signs were like pictographs, for the speaker pointed as nearly as possible to the thing that he desired to indicate, but later they became more and more conventional. For example, man, the erect animal, was indicated by throwing up the hand, with its back outward and the index finger extending upward. Woman was indicated by a sweeping downward movement of the hand at the side of the head with fingers extended to denote long hair or the combing of flowing locks. Among the plains Indians, the Dakotas, the main tribe of the Sioux family, are universally considered to have stood highest not only physically but mentally, and probably morally. Their bravery was never questioned, and they conquered or drove out every rival except the Chippewas. Their superiority was clearly seen in their system of government. Personal fitness and popularity determined chieftainship more than did heredity. The authority of the chief was limited by the Band Council, without whose approbation little or nothing could be accomplished. In one of the Dakota tribes, the Tetons, the policing of a village was confided to two or three officers who were appointed by the chief and who remained in power until their successors were appointed. Day and night they were always on the watch, and so arduous were their labors that their term of service was necessarily short. The brevity of their term, however, was atoned for by the greatness of their authority, for in the suppression of disturbances no resistance was suffered. Their persons were sacred, and if in the execution of their duty they struck even a chief of the second class they could not be punished.