How have courts interpreted medical malpractice cases in the past?

In Maertins v. Kaiser Foundation Hospitals (1958) 162 Cal.App.2d 661, 667, 328 P.2d 494, 498, the court stated in a medical malpractice case that, 'Even where plaintiff's negligence is proved it must be a proximate cause of the injuries to be a defense.' The court went on to say that, as in Preston, supra, it was, '. . . error to instruct the jury that they might consider plaintiff's delay in securing medical attention where there was no evidence that 'more prompt treatment would have obviated the operation'.'