? What do you mean dogs don't spit ivory? Where is the source?

Source: Ba Jin's Autumn V: "Happy, let me tell you: dogs can't spit ivory." Shuhua smiled naughtily. 」

Interpretation: Metaphorically, bad people can't say good things.

Pronunciation: t incarnation is not like a tooth.

Synonym: Dogs can't spit ivory.

Example:

1. Dogs don't spit ivory.

You two never spit ivory. Shall we redecorate our bedroom tonight?

Ivory cannot grow in a dog's mouth.

Your dog can't spit ivory.

5. Try to explain why shrimps and crabs spit bubbles in their mouths when they are not in the water.