Vampire biology is logical?
Warning: this post contains vampire bodily fluids. No, not blood. Not that either, you perv.
Dear paranormal & urban fantasy authors:
I agree with you that it is reasonable to say that vampire saliva may contain an anti-coagulant to keep the victim's blood liquidy and delicious (like mosquitoes do). It's also entirely possible that vampire saliva would have coagulant properties to prevent the victim (or in paranormal romance, the telepathically bound mate), from bleeding out, thus preserving the food supply.
But. Having two totally contradictory properties at the same time? Not so logical.
Dear paranormal & urban fantasy authors:
I agree with you that it is reasonable to say that vampire saliva may contain an anti-coagulant to keep the victim's blood liquidy and delicious (like mosquitoes do). It's also entirely possible that vampire saliva would have coagulant properties to prevent the victim (or in paranormal romance, the telepathically bound mate), from bleeding out, thus preserving the food supply.
But. Having two totally contradictory properties at the same time? Not so logical.