There nervous system isn ' t fully developed . I can ' t remember the name of the nerve off the top of my head , but around 5 or 6 years old they start gaining the ability to realize when they have a full bladder even at night . Couple this with training themselves to wake up and go to the bathroom when necessary , rather than relying on diapers and you have potty training . Source I ' m an M . L . T . Anatomyother medical classes <| sep |> By the same token , there should also be fewer grad students . Far fewer grad students . <| sep |> The Toronto Bridge TrollsHear Us Gouge <| sep |> Please let the agony end ! So same as usual <| sep |> Crappy jpeg compression helps to <| sep |> I fear no country . But that weather of yours . It scares me .