A student of the American Indian languages is naturally led to investigate the wide-spread use of the quinary-vigesimal system of counting which he meets in the whole territory from Alaska along the Pacific Coast to the Orinoco and the Amazon. One is tempted to begin with an inquiry into the concept of number in general, and a study of the binary, ternary, and quaternary systems of counting, but for these subjects I refer to the works of Conant, McGee, Villiers, Eells, and Gibbs. It is interesting to follow the evolution of the concept of number from the stage where there is practically no idea of it, to the counting in pairs, frequent among the Australian and South American tribes, and then to higher units. For the purpose of this paper, however, I shall assume that the stage of counting by fives, and the discovery that the five fingers of the hand are the most practical means of so counting, has been reached. This discovery naturally leads, almost immediately, to the extension of the quinary base to the decimal, i.e., the two hands, and then to the vigesimal, including also the toes of the feet.