The Horror!? 62: The Ape (1940)

Doctor Adrien is a not especially well-loved doctor in a small American town. He is secretly working on a serum to cure polio. His favorite patient is the paralyzed Frances Clifford, a young woman who reminds him quite a bit of his dead daughter, whom he couldn't save from the same illness. But he needs (you guessed it) human spinal fluid to produce a working serum. Coincidence helps him with a great way to cover up his tracks: A murderous gorilla (who looks better than one can expect from a Monogram feature) escapes from a traveling circus. Adrien is able to kill it. He hides this fact and proceeds to search for his involuntary fluid donors in a costume made out of dead gorilla. Yes, he must be a genius.
Before watching The Ape I didn't know that Boris Karloff (playing Adrien, of course) did his slumming for Monogram, like Lugosi. To my disappointment the film is neither good nor bad enough too be really interesting. Karloff's acting is subdued where uncontrolled hamming is asked for and Curt Siodmak's script seems as if its author was a little ashamed to write an ape movie, but sadly not ashamed enough to do something interesting with the sub-genre. So the film ends up in the very special hell of mediocrity.