a.    Plaintiff was pregnant and began to have cramps.  Covering doctor told her to stay in bed.  She began bleeding and doctor again said to stay in bed.  She eventually miscarried.  She sued the covering doctor and her doctor.  She sued the covering physician for negligence in failing to prevent miscarriage; she sued her obgyn claiming vicarious liability for the acts of the covering physician.
b.    HELD: Covering physician was not an agent of the obgyn.  One can be vicariously liable for acts of an agent if the principal controls the manner of performance and the result of the agent’s work.  Mere supervision is not sufficient.  Here, the obgyn had no control over the covering physician’s acts and treatments.
(1)    It is difficult to hold a physician responsible for the on-call doctor’s acts.