To know that he is always keeping a secret from her, that he has under all circumstances to conceal and hold fast a tender double tooth, which her sharpness is ever ready to twist out of his head, gives Mr. Snagsby, in her dentistical presence, much of the air of a dog who has a reservation from his master and will look anywhere rather than meet his eye.

To know that he is keeping a secret from her, like a tender tooth, which her sharpness is ever ready to twist out of his head, makes Mr. Snagsby unwilling to meet her eye.
