What is the common law test for a plaintiff in a medical malpractice case?

6 "Firmly rooted in the common law lies the concept that although one individual need do nothing to rescue another from peril not of that individual's own making, nevertheless, 'He who undertakes to do an act must do it with ... care.' [Citations.] '[I]f the defendant enters upon an affirmative course of conduct affecting the interests of another, he is regarded as assuming a duty to act, and will thereafter be liable for negligent acts or omissions....' [Citation.] 'If the conduct of the actor has brought him into a human relationship with another, of such character that sound social policy requires some affirmative action or some precaution on his part to avoid harm, the duty to act or take the precaution is imposed by law.... Where a person is under the special protection of another, the latter is bound to exercise reasonable care to prevent harm to him, and this duty may include protection from the dangerous conduct of third persons.' " (Schwartz v. Helms Bakery Limited (1967) 67 Cal.2d 232, 238-239, 60 Cal.Rptr. 510, 430 P.2d 68.)