13 Needles of Halloween #9

Similarly to how earlier in this series I described the scene where Rosemary gets sedated in Rosemary's Baby as the most disturbing moment in the film, I think a lot of people find the seemingly endless scenes in The Exorcist where Regan (Linda Blair) gets guinea-pigged for all of those medical tests to be among that films most upsetting moments -- I guess I won't come right out and call it "the most disturbing moment in the film" like I did for Rosemary because The Exorcist, dunno if you've heard, but The Exorcist has some moments. 

But it says something that Friedkin was not just talented enough to make these moments sting (and god do they with that ratcheting hammering soundtrack and Regan's cries) but that he was even smart enough to take so much time and care doing so, as they become integral to what makes the film such a masterpiece. The film shows science degrading and exhausting these people, beating them down to a place of absolute desperation -- it's the "modern" that alienates, proves pointless, and drives them into the arms of superstition and madness.