“We have to admit that their aristocracy was founded on better reasons than ours.”

In this quote, “their aristocracy” refers to the class distinctions among dogs. In Flush’s world, social hierarchies among the dogs exist, just as they do among people. Since dogs do not possess material wealth, however, the foundation of their hierarchy is different. Their social classes are tied to breeding, which is usually based on the utilitarian purpose of the dogs (as hunters, sheepdogs, and so forth). The quote claims that this is a more legitimate basis for a class system since it is based on merit and purpose, compared to human social classes, which are based on wealth inequities. Thus, this quote is a critique of the Class and Wealth Inequities in Victorian England.

“Two points he had in his favor indeed, great personal beauty […] and he was genuinely devoted to dogs.”

Mr. Mitford is not a good person, but, in Flush’s eyes, he redeems his character through his devotion to dogs and his good looks. This quote is a humorous take on how dogs might evaluate humans, which mirrors how humans themselves prize dogs for their looks and devotion. 

“For as long as Wimpole Street remains, civilization is secure.”

Wimpole Street is an upper-class neighborhood in London, and this quote holds it as a symbol of security and the continuation of “civilization” as Victorian Londoners understood it—the continuation of the established social order. However, this sentence is ironic since it—like the rest of Flush—is in fact a critique of this same social order and the idea that civilization’s security depends on entrenched social hierarchies.