In Chapter 7, the reader meets the talented Toby—a dog with a legendary nose whom Holmes and Watson recruit from a kennel in their search for the Wooden-Legged Man. Doyle uses a simile to emphasize Toby's uncanny skill at identifying and tracking scents:
He pushed the creosote handkerchief under the dog's nose, while the creature stood with its fluffy legs separated, and with a most comical cock to its head, like a connoisseur sniffing the bouquet of a famous vintage.
In this simile, Doyle compares Toby to a wine connoisseur—the way that Toby cocks his head when Holmes shows him the scented handkerchief appears similar to the tilt of a connoisseur in the act of smelling a fabulous wine. By personifying Toby in this playful way, Doyle ensures, much to the reader's delight, that the dog joins the colorful cast of The Sign of the Four as a character in his own right.
Earlier in the novel, the narrator compared Holmes to a bloodhound in his remarkable ability to doggedly follow clues as he solves his mysteries. In this case, however, Doyle flips the script and the narrator compares an actual hound to an intelligent, cultured man not unlike Holmes himself.
