The thumb-nail, curled up on itself in the womb, feels fear
The speaker is trying to convince his listeners that fear is more primal than any other emotions and feelings.
Why did he use thumb-nail as an example? I'm very confused.
Here is the context prior to the usage of "thumb-nail." It's taken from Clive Barker's short story, Dread
What?" said Cheryl.
"You mean things to do with bad experiences? Falling off your bike, or something like that?"
"Perhaps," Steve said.
"I find myself, sometimes, thinking of those pictures. Not deliberately, just when my concentration's idling. It's almost as though my mind went to them automatically." Quaid gave a little grunt of satisfaction. "Precisely," he said.
"Freud writes on that," said Cheryl.
"Freud," Cheryl repeated, this time making a performance of it, as though she were speaking to a child.
"Sigmund Freud: you may have heard of him." Quaid's lip curled with unrestrained contempt.
"Mother fixations don't answer the problem. The real terrors in me, in all of us, are pre-personality. Dread's there before we have any notion of ourselves as individuals. The thumb-nail, curled up on itself in the womb, feels fear."
"You remember do you?" said Cheryl.
"Maybe," Quaid replied, deadly serious