Alexander Koryagin to Ardith Hinton:

AH>> The head is part of the body.
AK> It can be understood that "This head is a part of this
AK> body" A criminal investigation. :)

Once the head has been severed from the body, it is no
longer part of it, but, in a sense, a part of it.  `part'
without an article denotes beloging in a general sense
rather than as a distinct element.  A thing may be a part of
another thing wihout beloging to it, as a severed head.

AK> And why not "a body"?

Becuase the statement is true of all bodies, and therefore
referes to the body in general, rather than as to a specific
body, such as your or mine.

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