Boris Karloff in THE APE (1940)
Dr. Bernard Adrian is a kindly mad scientist who seeks to cure a young woman's polio. He needs spinal fluid from a human to complete the formula for his experimental serum. Meanwhile, a vicious circus ape has broken out of its cage, and is terrorizing the townspeople. The Ape eventually breaks into Dr. Adrian's lab. The Doctor manages to kill it before any harm can come to himself. However, the spinal fluids he requires to perform his experiments have all been destroyed during the struggle between him and the Ape.