In the film, The Animatrix, specifically the Beyond section after the girl and the kids are quarantined, they return to the spot that had the glitch. I understand why she dropped the can (to see whether it will float), but what was the fixation with the blood?
There's a couple ways to interpret this scene.
The straightforward approach is to just assume she was cutting her hand with the can to see if maybe the 'power' they thought they had had to do with the can or with themselves, meaning maybe only organic matter (bodies, blood, etc) will work, but the blood still dripped to the ground.
The other more psychological approach is her realization that the place has no more 'magic' to it and the cutting is possibly an extreme way to feel something after having this area's special properties taken away from her.
Finally, it could just be dramatic effect and nothing more, though the stories of the Matrix have never been known to use imagery for something so basic, I believe.