preposition for body

I have seen a book that uses preposition in for legs and face (in face/ in leg). Is it safe to assume that preposition in is used for parts of the body? If not, please give me some guidelines.

Thanks.



Vladz

[Mister Micawber]

I'm afraid that a good bit of it is idiomatic, Vladz, but the preposition depends on the content-- does it seem more 'in'side the body part or 'on' the surface?--

He was wounded in the foot.
He has hair on his foot.
She showed surprise on her face.
I could see it in her eyes.
He is a little long in the tooth.