NOTES

my heart was poisoned with remorse

This may seem a strange usage, but it accords with the primary meaning of "remorse" in Mary Shelley's day. Johnson's Dictionary (1755) lists the following two definitions:

1. Pain of guilt
2. Tenderness; pity; sympathetick sorrow

In both cases, but particularly in the first, remorse involves a passionate suffering that could be likened to the action of poison.