How do the diction, irony, and suspense affect the short story "The Black Cat"?

All three of
these elements contribute to the horror of this story, "."  In the , theof the
narrator is suggestive of an astute and sensitive  mind: " I was noted for the docility and
humanity of my disposition."  He remarks upon the 'unselfish and self-sacrificing love of a
brute which goes directly to the heart of him who has ...tested the paltry friendship and
gossamer fidelity of mere man." Yet, in a grotesque turn of events, he kills both his wife
and his cat. 

Later, the contrast between the diction and the action becomes
more exaggerated, suggesting the arabesque of Poe:  grotesqueand terror. The forces of good
battle with evil in him until the horrific act, understated with ironic effect:  "But this
blow [of the axe onto the cat]was arrested by the hand of my wife.  Goaded by the
interference" he decides to kill her in his rage.  With grotesque calm he remarks,
"This hideous murder accomplished, I set ...with entire deliberation to the task of
concealing the body."  Calmly, the narrator chronicles the events following his wife's
death and his confidence in his "guiltlessness" until in his "bravado"
he knocks on the walls to prove their strength. In response is a "shriek, half of horror
and half of triumph."  With suspense mounting, the wall is torn down, revealing the horror
of a corpse and a "hideous beast."