The shaking of the bed. That's doubtless due to muscular spasms.
5 seconds sound clip from the The Exorcist movie soundboard.
You can hear this line at 00:48:24 in the Blu-ray version of the movie.
Quote context
[...]
- Lord, I am not worthy to receive you, but only say the word and I shall be healed.
- May the body of Christ bring me to everlasting life.
- Well, it's a symptom... of a type of disturbance in the chemical-electrical activity of the brain.
- In the case of your daughter, it's the temporal lobe. It's up here in the lateral part of the brain.
- The shaking of the bed. That's doubtless due to muscular spasms.
- Oh, no. No, no, that was no spasm.
- The problem with your daughter is not her bed. It's her brain.
- Lesion. Lesion in the temporal lobe. It's a kind of seizure disorder.
[...]