The tribal spirit, which maintains the unity of an elementary community,
is efficient just so long as personal contact between its members is
possible. If a tribal community becomes overgrown, so that mutual
contact between its members is rendered impossible, then a manifestation
of a different nature appears--that of disruption or swarming. The
disintegrating tendency is just as much a part of Nature's evolutionary
contrivance as is the isolating and unifying effect of the tribal
spirit. For breeding purposes the group must be kept within certain
bounds. Modern man has overcome the tendency to disruption on the part
of massed communities by the invention of means of rapid
intercommunication. The daily press, the hourly post, and a network of
electric wires can bind a hundred millions of modern people into a
sentient tribal web.