Quotations

Q. I am having trouble understanding the structure of the following example (CMOS 13.53): “Everyone knows that the Declaration of Independence begins with the sentence ‘When, in the course of human events . . .’ But how many people can recite more than the first few lines of the document?” Are these intended to be two sentences? If so, why would there be no closing period after the ellipsis points and closing quotation mark (i.e., before “But”)? If they are one sentence, why would “But” be capitalized? I’m missing something—or misunderstanding, perhaps. Please help.

A. They are two sentences. There is no period at the end of the first sentence because the quotation trails off before it reaches grammatical completion. If the quotation were a complete sentence, a period would be called for: “Everyone knows that the song begins with the sentence ‘We’re a ménage à trois: just moi—et moi—et moi.’ But how many people can recite more than the first few lines?”