Aeschylus, Prometheus Bound 932 ff (trans. Weir Smyth) (Greek tragedy C5th .) :
"Chorus : How is it that you are not afraid to utter such taunts [against Zeus]?
Prometheus : Why should I fear since I am fated not to die?
Chorus : But he might inflict on you an ordeal even more bitter than this.
Prometheus : Let him, for all I care! I am prepared for anything.
Choru s: Wise are they who do homage to Adrasteia (the Inescapable)."
[. Adrasteia is Nemesis. To bow down before Adrasteia means seeking to avert, by some gesture of humility, the evil consequences of boastful speech.]
It has been suggested that snakes evolved the mechanisms necessary for venom formation and delivery sometime during the Miocene epoch.  During the mid- Tertiary , most snakes were large ambush predators belonging to the superfamily Henophidia , which use constriction to kill their prey. As open grasslands replaced forested areas in parts of the world, some snake families evolved to become smaller and thus more agile. However, subduing and killing prey became more difficult for the smaller snakes, leading to the evolution of snake venom.  Other research on Toxicofera , a hypothetical clade thought to be ancestral to most living reptiles, suggests an earlier time frame for the evolution of snake venom, possibly to the order of tens of millions of years, during the Late Cretaceous . 
Man, that thing is just great!!! I'll DEFINITELY be trying this sometime!!! I figure you can use a necklace too, well, anything that can be washed. I wish V_day was back around.
My girlfriend is going to be gone most of the summer, I think I'll try letting her have my heart to take with her. =D
As Sergeant Crayon said, you could always freeze the blood bag, then simply tear the bag off, and stick the frozen blood in the heart. I'll try some experiments with freezing that mixture and putting it in jello. You just want to make sure the blood is frozen long enough to the gelatin around it to harden, so it doesn't all mix together. but I'm sure the cold from the blood will cure the gelatin around it fast enough to keep the insides from becoming a big mess!
In the beginning, I was thinking you were going to have us do a bit at a time until we had a good 1/2 inch on every surface, then just fill that with blood.