What standard of care does a surgeon need to meet with a patient?

Rand, J., set out the duty and standard of care in relation to medical practitioners in Wilson v. Swanson (1956), 1956 CanLII 1 (SCC), 5 D.L.R.(2d) 113 (S.C.C.), at p. 119, as follows: "In the presence of such a delicate balance of factors, the surgeon is placed in a situation of extreme difficulty; whatever is done runs many hazards from causes which may only be guessed at; what standard does the law require of him in meeting it? What the surgeon by his ordinary engagement undertakes with the patient is that he possesses the skill, knowledge and judgment of the generality or average of the special group or class of technicians to which he belongs and will faithfully exercise them."