> Stoker, a theatre manager with no medical background, somehow described the basic mechanism of heterochronic parabiosis
Just to pick a nit...
Stoker's story was inspired by "The Vampyre" by physician John Polidori, who doubtless knew whatever his contemporary medics knew about blood.
Polidori, Lord Byron, and Mary Shelley told scary stories to each other by Lake Geneva in 1816, the "year without a summer". It couldn't get more gothic.
https://publicdomainreview.org/essay/the-poet-the-physician-...
It is worthy of note that John Polidori's model for a vampire was, in fact, Lord Byron.
Lord Byron's death was a result of what the medical profession then thought that they knew about blood. Namely that blood-letting was a worthwhile medical treatment.