(⑤).Tribes A、B:“鸡、犬之声相闻， 民至老死不相往来” Tribe A as system -Closed system Tribe A+B as sytems -Isolated system 上游充通大粤 March 3,2018 11 SHANGHAI JLAO TONG UNIVERSITYMarch 3, 2018 11 (5). Tribes A、B:“鸡、犬之声相闻， 民至老死不相往来” A B Tribe A as system Tribe A+B as sytems — Closed system — Isolated system