[PW] why dewey decimal system not use 040s?

[Bruce Greeley]

Hi all,
 
I'm a librarian who consults your wisdom when stumped in other channels. My daughter (a budding librarian?) wants to know why the dewey decimal system doesn't use the 040s series of numbers now...?
 
I think I've figured out that they were last used in the 16th edition of the catalog (in the 1960s?) but want to know what topics were cataloged in this number series and why it may have been discontinued (and where they were 'absorbed'...?)
 
I'm not a member of this list so would love if you could email me directly (though will check the archives too).
 
I think I found out that the number 574 is also unassigned too now, so I guess what happened to that one (and any others now unused).
 
thanks much for any illumination!
 
Bruce Greeley
Managing Librarian
Valley View/Southcenter/Fairwood
206-242-6044