P has sued D, her anesthesiologist. The anesthesiologist positions and cushions the patient's arm to avoid nerve compression injury during surgery. After a bilateral mastectomy, P experienced numbness in her right arm. The numbness subsequently was diagnosed as ulnar neuropathy, a condition marked in her case by degenerative nerve damage to the fourth and fifth fingers of her right hand. P alleged separate counts of medical negligence, battery, and res ipsa loquitur. P's expert testified that the ulnar nerve can be injured if it is compressed. The expert believed that in all probability, the injury occurred while P was under anesthesia for [the] surgery' and that such injury was totally preventable by proper care. He testified that the ultimate responsibility for protection against injury lies with the anesthesiologist, who should properly position and cushion the arm to avoid compression and should monitor the arm during surgery to be sure that proper positioning and cushioning are maintained while the patient is unconscious. At the close, the judge refused to forward the case on the theory of res ipsa loquitur. The Court of Appeals affirmed. This appeal resulted.