Ybarra (P) was diagnosed with an appendicitis by Dr. Tilley (D1). D1 arranged for an appendectomy by Dr. Spangard (D2) at a hospital owned and operated by Dr. Swift (D3). P was taken into the operating room by nurse Gislor (D4) and anesthetized by Dr. Reser (D5). D5 laid P back with the top of his shoulders against two hard objects. P awoke the next morning attended by Thompson (D6) and another nurse and felt a sharp pain between his neck and his right shoulder. The pain spread down his arm and continued to grow worse. P developed paralysis and atrophy of the muscles around the shoulder. D5 and the nurses were employees of D3. D1 and D2 were independent contractors. P sued and claimed res ipsa loquitur. The medical personnel claimed that res ipsa loquitur should not apply against them; there was no showing that the act of any particular defendant, nor any particular instrumentality, was the cause thereof. Ds claimed that the injury could have resulted from the actions of any of the Ds and thus the doctrine cannot be applied. Ds also claimed that there were several instrumentalities involved and any of them may have caused the injury. The trial court awarded Ds a nonsuit. P appealed.