In the following passage from Chapter 38, Mr. Squeers complains about Smike's "ungrateful" behavior, utilizing both metaphor and allusion to do so:

Mrs Squeers has been his mother, grandmother, aunt, – Ah! and I may say uncle too, all in one. She never cottoned to anybody except them two engaging and delightful boys of yours, as she cottoned to this chap. What’s my return? What’s come of my milk of human kindness? It turns into curds and whey when I look at him.

When Mr. Squeers refers to the "milk of human kindness" in this passage, Dickens is alluding to a prominent passage from Macbeth (Act I, scene 5, lines 15-17): "Yet I do fear thy nature. / It is too full o’ th’ milk of human kindness."

Mr. Squeers also utilizes metaphor in this passage, angrily asserting that Smike is ungrateful to himself and Mrs. Squeers for all that they have done for him. Mr. Squeers declares that his "milk of human kindness," or his compassion, has curdled into bitterness and anger (curds and whey) due to Smike's alleged behavior. Mr. Squeers feels that Smike owes him something, despite the fact that Squeers has been abusing and taking advantage of Smike for years. This entitlement is a strong feature of Mr. Squeers's character.