What? That blood brought a tribble back to life.
Blood is a key element in the healing process, even in normal humans.
1) Khan has remarkable recuperative abilities. They say so in "Space Seed". He brings himself back from near death.
KIRK: Bones?
MCCOY: He'll live.
KIRK: My compliments.
MCCOY: No, I'm good, but not that good. There's something inside this man that refuses to accept death. Look at that. Even as he is now, his heart valve action has twice the power of yours and mine. Lung efficiency is fifty percent better.
(McGivers enters)
KIRK: An improved breed of human. That's what the Eugenics War was all about.
MCCOY: I'd estimate he could lift us both with one arm. It will be interesting to see if his brain matches his body.
2) The little girl in act one is saved by Khan's blood.
3) The tribble is brought back to life by Khan's blood.
Connect the dots.