Conversation so far:
What is The Citadel in relation to A. J. Cronin?
The Citadel is a novel by A. J. Cronin, first published in 1937, which was groundbreaking in its treatment of the contentious theme of medical ethics.

Question: How did Cronin draw influence from it?
Self-contained rewrite: How did A. J. Cronin draw influence from his novel The Citadel?