Guitarist Phillips is using the bow on this song, too like in "Painter Man" as stated below by others here down below. Brilliant stuff for it's time, I think. It was 1966, who else was doing that?
I'll tell you who - no one. Light years before Jimmy Page ever thought of it and yet somehow he gets all the credit for doing it, too. Bullshit, I say. But the "Zepp" Guys did "borrow" a lot, didn't they?
That's a story for another day. In fact, The Mark Four / The Creation were pioneers of guitar feedback / reverb etc all the way back to 1964. Criminally underrated, another shoulda, coulda, woulda tale ; these guys should have had more fame.