Answer:
The sentence "And it was the memory, that came up now" (line 123) shows the narrator is transitioning to a flashback, as it sets the premise of the flashback. This sentence hints that the narrator is about to recall a memory that is linked to the current situation, which is the sound of the heart beating. This sentence marks the shift from the present to the past. The flashback provides a deeper understanding of the narrator's situation and offers context for his thoughts and behaviors. The shift from the present to the past shows the power of memory and how it shaped the narrator's thoughts and behavior. This transition to a flashback shows the power of the past and how it continues to affect the present.