关于who(se),which引导定语从句的一个问题

大家知道,关系代词 who,whose,which 可引导定语从句。许多语法书和课本都讲“who,whose 指人,which 指物”,其实也不尽然。who,whose 也可指“动物,国家”等,which也可指“人”。请看下列例句: 1.Our dog,who had been lost for two days,wasfound and brought home by a policeman. 我们那只狗,丢失两天后被一位警察找到并送回家来了。