(1) An actor may be liable if the actor's negligence is a substantial factor in causing an injury, and the actor is not relieved of liability because of the intervening act of a third person if such act was reasonably foreseeable at the time of the original negligent conduct. (Vesely v. Sager (1971) 5 Cal. 3d 153, 163 95 Cal. Rptr. 623, 486 P.2d 151). "The foreseeability required is of the risk of harm, not of the particular intervening act." (Torres v. Xomox Corp. (1996) 49 Cal. App. 4th 1, 18 56 Cal. Rptr. 2d 455). (2) to determine that " 'a negligent actor is liable for another's harm, it is necessary not only that the actor's conduct be negligent toward the other, but also that the negligence of the actor be a legal cause of the other's harm.' 'Legal cause' exists if the actor's conduct is a 'substantial factor' in bringing about the harm and there is no rule of law relieving the actor from liability." (Nola M. v. University of Southern California (1993) 16 Cal. App. 4th 421, 427 20 Cal. Rptr. 2d 97). (3) It has long been the rule that a tortfeasor responsible for the original accident is also liable for injuries or death occurring during the course of medical treatment to treat injuries suffered in that accident. In Ash v. Mortensen (1944) 24 Cal. 2d 654 150 P.2d 876, the Supreme Court stated: "It is settled that where one who has suffered personal injuries by reason of the tortious act of another exercises due care in securing the services of a doctor and his injuries are aggravated by the negligence of such doctor, the law regards the act of the original wrongdoer as a proximate cause of the damages flowing from the subsequent negligent medical treatment and holds him liable therefor." (Id. at p. 657, citing Dewhirst v. Leopold (1924) 194 Cal. 424, 433 229 P. 30).