ANTHROPOLOGY: C. WISSLER 
401 
sensitivity to potential-differences is practicaUy independent of the size 
of the instrument. The last model made, with a needle 1.8 cm. long, 
has a capacity of 9 cm., but this could without difficulty be halved by 
reducing the size of the instrument; and it might be halved again by 
omitting one end of the needle and the pair of sectors below it. 
Although the sensitivity of the electrometer (with the very efficient 
optical system used) is theoretically great enough to detect 10~® volt, 
it has not as yet been made steady enough to detect an isolated poten- 
tial-difference of less than about 3xlO~^ volt. 
The details of the construction of the instrument and the results of 
measurements made with it, together with a consideration of the cause 
of the residual unsteadiness will be discussed in a more extended article 
to be published shortly, 
THE DISTRIBUTION AND FUNCTIONS OF TRIBAL SOCIETIES 
AMONG THE PLAINS INDIANS: A PRELIMINARY REPORT 
By Clark Wissler 
AMERICAN MUSEUM OF NATURAL HISTORY. NEW YORK 
Presented to the Academy, June 2, 1915 
For several years the American Museum of Natural History has been 
engaged in systematic anthropological field-work among the surviving 
Indians of the great Plains area in North America pertain'ng to one 
definite problem, viz., the distribution and functions of tribal societies. 
Early observers noted the existence of societies, chiefly for men, which 
within the tribe seemed to be correlated and in some cases organized into 
progressive series, or ranks. Some data more or less fragmentary were 
recorded by Lewis and Clark, Catlin, and Maximilian in early days, 
and later by Grinnell and J. O. Dorsey. The first serious investigation of 
such societies was undertaken by A. L. Kroeber among the Arapaho. 
This was followed by work among the Cheyenne by G. A. Dorsey, 
among the Assiniboin by R. H. Lowie, and among the Blackfoot by me. 
These pioneer studies revealed such striking similarities between these 
four tribal systems of societies as to suggest a case of culture diffusion. 
The significance of the problem may appear from the following brief 
statement; two investigators had previously made special use of what 
data were then available on these societies in their respective efforts 
to explain such phenomena as manifestations of ar^yet to be discovered 
law of social evolution. ^ In each case the method was the same, one 
employed by many ethnologists and sociologists; viz., to collect examples 
of tribal societies from several parts of the world and to theoretically 
