If you plug a bass into a guitar amp? Well, it works... but it's not ideal. a word of caution, if you do a lot of slap bass stuff, you'll want a compressor in line between the two, as the dynamic range of a bass goes from quite a bit lower than a normal guitar for unslapped stuff to WAY above while slapping, and aside from sounding horribly uneven, I wouldn't think it'd be good for the amp to hit it with anything that hot. Besides, you'll drive the amp in and out of distortion, which would sound odd, at least...
At the same time, a Fender Bassman was originally intended as a bass amp, so it all depends what sort of stuff you're playing.
-D