"Good Blood"
The most significant metaphor in the book is probably the simple two-word phrase "good blood." It is expressed explicitly in this form only a couple of times over the entire breadth of the novel, but its metaphorical meaning is a foundation of the entire plot. "Good blood" is a metaphor for supposedly pure genealogical aristocratic heritage. It is a code that tells like-mind believers you are superior.
Dr. Thorne
The narrator spends a lengthy paragraph in outlining the philosophical approach to tendering medical services in exchange for recompense as it relates to Dr. Thorne. Ultimately, the narrator asserts that many of the villagers believe that "a physician should take his fee without letting his left hand know what his right hand was doing." This is a metaphorical image strongly suggesting that a doctor should be more concerned with dispensing care than he is with receiving payment.
Secrets and Lies
As with any story that takes place in a small town, there are secrets well-kept that must inevitably get out. In keeping with the decision to title the book after the local physician, the metaphor that addresses this reality is a medical one. "Wounds sometimes must be opened in order that they may be healed." In this particular case, as well as many others throughout the story, the metaphor specifically relates to the consequences of illegitimacy of a major character.
Hypocrisy
Dr. Filgrave is described as a physician who really enjoys the monetary earnings side of his chosen career. Unfortunately for him, he also values his dignity. "He was angry also; and like all angry men, he loved his grievance." The metaphorical passion expressed here refers to Filgrave's love of money coming into conflict with his right to expect respectful treatment. When the respect fails to come, the money feels like an insult. So it comes down to what he loves more: proper payment or the hypocritically good feeling that comes with being angry over being disrespected.
Men
Although it is more openly discussed, the concept of the alpha male is hardly a latter-day invention. "Between the alpha of the whole alphabet, and him whom he could not but regard as the omega! ... Why he would think of it as though a lamb and a wolf were to stand at the altar together." These thoughts of Dr. Thorne in response to the shocking news of a potential engagement of Mary Thorne and Sir Louis Scatcherd may come as a revelation to modern readers. This is far less the case with the subsequent simile of the lamb and wolf, of course, but while alpha males are omnipresent in social discourse today, the lamb and wolf metaphorical comparison is far less common.
