I have a house plant that is 10 years old. I recieved it after my Grandfather died in a funeral arrangement and I cherish it. My husband's new puppy (devildog) dug it out of it's pot and shredded the roots. My husband tried to put it back together. Now it is dying very fast. I don't know what kind of plant it is . It is about 4 ft. tall and looks like a dark green corn stalk. If it cannot be saved can I cut the top off and get it to root somehow since it is dying form the bottom up?

What I would do is take the plant and cut the stalk on a slight angle. Dip it into a rooting hormone, You can get this any nursury, or garden center. Then put it into some moist potting soil. Keep the potting soil poist for a few weeks and it will start to reroot itself. Do this soon before the plant goes beyond repair.
Hope this helps

Mike