The Black Cat
How we cite our quotes:
I grew, day by day, more moody, more irritable, more regardless of the feelings of others. (6)
These are the beginning stages of the man's hideous psychological transformation. He connects it to alcohol (though perhaps there is more going on). When alcohol and/or drugs play a central role in a story, transformation is probably featured as well. The nature of the transformation depends on the story. Here the transformation is altogether negative.
I knew myself no longer. (7)
Most people experience this feeling at some point or another, especially when in the midst of changing. Here the narrator is stressing the degree of transformation, hoping we remember that he was a nice guy in high school.
I took from my waistcoat pocket a pen-knife, opened it, grasped the poor beast by the throat, and deliberately cut one of its eyes from the socket! (7)
This is a transformative moment for both Pluto and the narrator. The narrator crosses a previously uncrossed line of violence. His act is irrevocable. Pluto's physical transformation will be a constant reminder of crossing the line. Eye problems and eye violence are often featured in stories of transformation. They signal transformed vision in the characters, and hope to signal transformation in the reader.