OS X V10.5 Leopard :: Junk Button Disappeared And Filtering Stopped In Mail 4.5

I am using Mail 4.5. I used to have a Junk button next to the Delete button. I would select a long list of messages and click the Junk button. I was making adjustments in my Preferences (to stop certain filters), and must have done something to make that button disappear. Also, it seems to have stopped filtering junk. My Junk Mail preferences still show: Enable junk mail filtering, When junk mail arrives, move it to the junk mailbox, and all the rest of the boxes are checked.

Info:
Mac Pro, Mac OS X (10.5.8), 2x3 GHz Dual-core Intel, 750GB+5TB