Chapter 6: Vicarious liability of hospitals for negligence of medical staff

What are the contrasting traditional views versus modern movements toward expansion of liability under agency principles?

Book reference is Health Law 8th Edition by Furrow, Greaney, Johnson, Jost, Schwartz, Clark, Brown, Gatter, King, Pendo:

Two elements are required to establish an agency relationship: 1) the principal must consent, either expressly or impliedly, to the agent's acting on the principal's behalf and (2) the agent must be subject to the principal's control. In a hospital-physician relationship, the primary focus is on whether the hospital generally controlled, or had the right to control the conduct of the doctor in his work performed at the hospital.