To be honest, if you're going by modern medical/biological sciences, none. However, for period readers, Shelley shares a number of convincing details. The most important of these is the use of electricity in bringing the creature to life. A British scientist from the period named Andrew Crosse did experiments in galvanism, which showed that electrical shocks could cause muscle tissues to twitch even after a body was technically dead.
More generally, Victor studied "natural philosophy" (a general term at the time for science), physiology, chemistry, and other older writers, such as alchemists. These writers are discredited now, but they sought similar powers, and so might be considered convincing.