Back in All-American Comics #24 (March 1941), the issue had a promotional ad for two new characters who would be joining the likes of Green Lantern, The Atom, Mutt & Jeff, plus other features in that comic book:
Dr. Mid-Nite's feature started in issue #25, but in the following issue (All-American Comics #26, cover-dated May 1941), Sargon the Sorcerer began his adventures!
From issue #26:
to be continued . . .