Whether or not it's human, whether they've cut it with anything to prevent coagulation, whether it's carrying any pathogens... there's a lot of information hidden in blood. More interesting than helpful, maybe.
[ He's pretty well enamoured at the moment, clearly - though he does manage to glance with a little shrug of what he purports as sympathy to Rudy. ]
The stakes of cross-contamination did suddenly get a lot higher.