Otis Adelbert Kline 
The Call of the Savage [EPUB ebook] 

Far from the world of his white parents, the sixteen-year-old youth, Jan, was raised in a cage under the watchful eye of half-crazed Dr. Bracken. Guided by his foster mother, Chicma the Chimpanzee, Jan was destined to execute the doctor’s fanatical plot for revenge against Jan’s real mother. A monster with the mind of an ape and the body of a man, that was his part in Bracken’s twisted scheme. But just on the eve of the intended onslaught, Jan and Chicma escaped to the jungle and emerged near the Lost Empire of Mu. There, Jan must do battle with the gigantic puma, the grotesque thunder bird, and the god-monster Sebek. With all his fighting skill, there remained only one challenge to Jan: trace his origins and locate his man-parents.