Irony in The Adventure of the Speckled Band

Irony Examples in The Adventure of the Speckled Band:

The Adventure of the Speckled Band 1

"That and a tooth-brush are, I think, all that we need...."   (The Adventure of the Speckled Band)

One suspects this list—the pistol and the toothbrush—is meant to be a humorous touch. Spoiler: the toothbrush is never mentioned again in the story. Whether Holmes anticipated needing it is unclear. In retrospect, this looks like a joke.