'Black people don't feel pain, therefore why waste the anesthesia?'

J. Marion Sims was a prominent figure in medical science in the US, known as the "Father of Modern Gynecology". He contributed revolutionary tools and techniques to the field of medicine, but his achievements were made on brutal human experimentation. He operated on black women without any anesthetic, but white women were anesthetized, so how low was the status of blacks in the US? How miserable were the lives of black slaves?