Thanks for the response. I believe I hear the following for the 220v stuff
(and I'm not talking code here, but practicality} :

1. The neutral is considered a ground return, in relation to the two hot
220v legs.

2. The neutral may in fact be connected to earth ground at some point along
its way.

3. The 4th wire used in some setups is somewhat redundant, as it could also
be incorporated in with the neutral, thereby eliminating the need for the
4th wire

4. Where a 4th wire is used on a 220v setup, that wire is simply a ground
continuity thing for safety purposes.

Is all this correct? If so, I think I understand it now.