The Mind Master

"The Mind Master" is a sequel to the short science fiction novel "Manape the Mighty." Three months after the events in Africa, Lee Bentley and Ellen Estabrook are back in New York - and so is Professor Barter, who is not dead, but is very much alive and equipped with heat and disintegrator rays, a far viewer, and brain implants that permit long-distance hypnotic control.
"Certainly it was a far cry from the African jungles where, for the space of a ghastly nightmare, Ellen had been a captive of the apes and Bentley himself had had a horrible adventure.
Caleb Barter, a mad scientist, had drugged him and exchanged his brain with that of an ape, and for hours Bentley had roamed the jungles hidden in the great hairy body, the only part of him remaining "Bentley" being the Bentley brain which Barter had placed in the apes skull-pan. Bentley would never forget the horror of that grim awakening, in which he had found himself walking on bent knuckles, his voice the fighting bellow of a giant anthropoid.
Yes, it was a far cry from the African jungles to populous Manhattan.