“Ya see, when a man bleeds, it’s just tissue, but blood from one of you Things won’t obey when it’s attacked. It’ll try and survive… crawl away from a hot needle, say.”
It’s the line that launches one of the most iconic scenes in all Horror Cinema, one that, amid the many notoriously gruesome transformation effects found in The Thing, makes effective use of some very humble lab equipment to ratchet up the tension.
With the research team’s medical men either incarcerated or dead, it falls to Outpost 31’s kick-ass chopper pilot R.J. MacReady (Kurt Russell) to rig a blood test of his own devising as a means of telling who’s human and who’s Thing. Mac is no medic, so he uses what he can find – some petri dishes diligently labelled with each man’s name and a coil of wire heated by the business end of his flame thrower. The idea is to gather blood samples from each of the surviving men, dip the hot wire in and see what happens.
We the audience don’t really know what to expect, so Carpenter uses a series of reaction shots of his characters to indicate that the result of Mac’s first attempt to test a sample – a thin, hissing plume of rising smoke when the wire makes contact – is the sign that the man this blood belongs to is human. That’s fine, but we still don’t know how Thing blood is going to react to the wire. We have a healthy suspicion that eventually one of the samples will definitely react differently, and from the evidence that we’ve been presented with in the run-up to the scene we might well have our own theories as to which man’s sample it will be.
When the moment comes Mac is holding the labelled petri dish containing the alien liquid right under our noses, but the reaction is so brief and violent that it takes eagle eyes to notice that the hand in which Mac is holding the dish is, somewhat ironically, not human tissue.
The effects team rigged the dish so that a large piece of Thing matter would pop up rapidly to show that it clearly didn’t like the heat from the wire. In order to achieve this they used a dummy hand in place of Kurt Russell’s own. Watch it again and see if you can spot the manikin fingers clutching the dish.