I tried to kill him for the purpose of strengthening my vital powers by the assimilation with my own body of his life through the medium of his blood – relying, of course, upon the Scriptural phrase, "For the blood is the life."
– Bram Stoker
Dracula, Chapter 18. Renfield explains to Dr. Seward why he eats animals and tried to kill a person. He believes that to consume someone else’s blood to to consume some vital part of their life, giving you vital powers. Blood represents life.