Stanley Weinbaum 
The Adaptive Ultimate [EPUB ebook] 

Dr. Daniel Scott approaches his colleague, Dr. Herman Bach of Grand Mercy Hospital, looking for a human test subject. Scott claims that recovering from a disease or injury is merely a matter of adaptation. He has derived a serum from fruit flies, the most adaptable creatures he could find. Bach is skeptical, but has a patient only hours from death due to tuberculosis (at the time an incurable disease). With nothing to lose, a drab, plain woman named Kyra Zelas agrees to the treatment. The results are beyond Scott's wildest dreams.