This Doctor foreshadows the upcoming danger and eventual madness that Marlow will face in the interior. Measuring Marlow’s skull is something akin to taking scientific observations of his brain. This may seem unnecessary until we remember that Kurtz went into the jungle as "original Kurtz" and came out one of many "shades of Kurtz." Will Marlow, too, be irrevocably changed from his journey into a murderous and obsessed madman? That’s the pessimistic question asked by the head-measuring Doctor.