What does Dr. Armstrong say about the death of Louisa Cleese? What does he think about it?

From the text:

“Drunk - that’s what it was - drunk... And I operated! Nerves all to pieces - hands shaking. I killed her, all right. Poor devil - elderly woman - simple job if I’d been sober. Lucky for me there’s loyalty in our profession. The Sister knew, of course - but she held her tongue, God, it gave me a shock! Pulled me up. But who could have known about it - after all these years?”