William Somerset Maugham was the one who said, "The novel is a picture of real life and manners, and of the time in which it was written".
As with any author's decision to use 1st person, her intention most likely -- in this story -- was to get her readers to go along for the ride into madness and cultivate a certain amount of sympathy for the narrator and her plight. The constant use of "I" puts readers in the narrator’s head and allows them to empathize with her.
The answer you are looking for is:
Simile, metaphor, hyperbole, and also personification but thats not up there.
Hope that helps!!
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This is a quote from "The Secret Life of Walter Mitty", and it is a made-up term. He is not a skilled surgeon, so he made up the term obstreosis (a word that does not even exist), duct is like a passage, the same way as tract. So this "disease" makes no sense and does not exist.