Mouse wheel doesn't scroll in emacs 23.4.1 in Ubuntu 13.04

Mouse wheel doesn't scroll in emacs 23.4.1 in Ubuntu 13.04

Scrolling with the mouse wheel doesn't work for me in emacs. When I try, I
get the messages:
mouse-4 [[or mouse-5]] is undefined
I tried M-x mouse-wheel-mode, but get the error:
Symbol's value as variable is void: mouse-wheel-mode



Possibly useful information:
I recently installed Ubuntu 13.04, dual-booted with Windows 8 on my laptop.
I installed emacs using apt-get install emacs, which pulled version 23.4.1
I'm a fairly comfortable Linux user, but I have very little system
management experience so it's entirely possible I'm missing something
obvious.