Similar in principle to the enclosing of parenthetic expressions between commas is the setting off by commas of phrases or dependent clauses preceding or following the main clause of a sentence.
Bartle kept his eye on the moving figure till it passed into the darkness, while Vixen, in a state of divided affection, had twice run back to the house to bestow a parenthetic lick on her puppies.
间的规则，
主要
德（
）
黑暗中，而泼妇则
，
她的小狗舔了舔。
