I remember his words on full-moon nights in Addis Ababa when knives are flashing and rocks and bullets are flying, and when I feel as if I am standing in an abattoir and not in Operating Theater 3, my skin flecked with the grist and blood of strangers. I remember. (P.26)
The prologue has Marion explaining where he is now (Addis Ababa, clearly in a war zone) but also letting us know what the novel is going to be about: it's going to be all about his memory. Even while he's dodging bullets in the present, Marion is actually reliving the past, over and over again.
At such moments I remember to thank my twin brother, Shiva—Dr. Shiva Praise Stone—to seek him out, to find his reflection in the glass panel that separates the two operating theaters, and to nod my thanks because he allows me to be what I am today. (P.28)
Marion's brother is a memory because he died. We don't know yet how or why, but this mention shows us that the twins have split. The reflection probably looks just like Shiva, since Marion and Shiva were identical twins, but it's still just a piece of glass. Marion can't get to his reflection, just like he can't go back in time to get to Shiva.
In the ensuing seven years that she lived and worked at Missing Hospital, Sister Mary Joseph Praise rarely spoke about her voyage and never about her time in Aden. (1.1.83)
Whereas Marion has decided to sit down and write his entire past, including memories that don't even belong to him, his mother had a different approach. She experienced a terrible trauma in Aden, probably rape and kidnapping, and decided to bury her memories of the past, never looking back.
Such a crucial gap in the history, especially that of a short life, calls attention to itself. A biographer, or a son, must dig deep. Perhaps she knew that the side effect of such a quest was that I'd learn medicine, or that I would find Thomas Stone. (1.1.84)
Marion never got to know his mother, so he has no memories of her. This "gap" must gnaw at him, because he decides to fill it up with information he gathers from a historical investigation. What he hasn't experienced he wants to learn by reading and talking to others who did.
As abruptly as it started, in two days, no more than three, the spell would be over, and after a very long sleep Stone would be back at work as if nothing had happened, never making any reference to how he'd inconvenienced the hospital, the memory of it erased. (1.2.42)
Whereas Sister Mary Joseph Praise forgets her past because it is so painful to her, Dr. Stone forgets his past because it is so painful to others. His drunken binges cause considerable damage to the hospital and its staff, but he never even acknowledges them.
When, years later, she'd look back at this moment of change, look at it clinically ("Milk the history! Exactly when and exactly how did it start? Onset is everything! In the anamnesis is the diagnosis!" as her professor would say), she would see that her transformation actually took place over many months. However, it was only as she was falling out of the sky over the Bab al-Mandab that she understood that change had come. (1.3.44)
The word anamnesis comes from Greek and means remembrance or reminiscence. In this case, however, it refers to a medical history. The doctor's job isn't just to work with the body in front of her, but also to ask the patient for memories of symptoms and pain in order to fit the past into the present and make a diagnosis.
Perhaps it was because the emperor was still on her mind, and because her taxi was at the intersection where, in place of the string of shops, there once stood a gallows, but suddenly Hema was thinking about a scene that haunted her. (1.6.50)
Isn't it funny when space and time kind of implode, like in this scene? Hema has lived in Addis Ababa for years, but for some reason, today, when she drives past a certain spot, she is transported back in time to the memory of that spot several years ago. Of course, it's a traumatic memory of a hanging, so it's not such a surprise that it could creep up, but it's still interesting how place triggers memory.
He turned to leave again, glancing around as if to seal in his memory this place in which he'd polished and elevated his art, this place that he'd furnished to suit his needs and that he thought was his real home. He took it all in because he knew he'd never ever return. (1.10.49)
We don't often get the chance to know that an experience is our last one. Stone is making the decision to leave Missing (and the pain of losing Sister Mary Joseph Praise) behind him, and so he's able to program his own memories of the place. This vision of the place will haunt him for years to come.
Ghosh recognized the song, a very popular one. It was called "Tizita"; there was no single equivalent English word. Tizita meant "memory tinged with regret." Was there any other kind, Ghosh wondered. (2.11.85)
Many cultures have words for nostalgia, but the word tizita has a special hint of remorse or regret in it. Even though Ghosh is not Ethiopian, he seems to have adopted its attitude toward the past, in which all memories must have regrets.
She was mourning […] the passage of the years. She'd come to Addis Ababa from England after getting restless teaching in a convent school and running the student infirmary; she'd accepted a post with Sudan Interior Mission to work in Harrar, Ethiopia. In Addis, she found her orders were canceled because the Italians had attacked, and so she had simply attached herself to a small hospital all but abandoned by the American Protestants. (2.12.48)
Matron, like Stone on his way out of the hospital, is very conscious of the way the past is building up behind her, pressing in on her and stealing her attention from the present. It must be strange to look back on events that, at the time, couldn't have the weight they do now that they are in the past.