Cow tongue?

I honestly wasn't sure how the dogs would take to it but oh wow they REALLY enjoyed it.  It was their first time eating it and we served it as a side to their nightly veggie pattie.  I have fed more to both tonight because we had the tongue that needed to be used soon.  So tomorrow they will get more.  I haven't read up a lot about the muscle meat (I'm assuming that the tongue is considered a muscle meat).  So will do that tonight before I go too overboard on it.  The butcher I have has TONS of them and he's selling them to me A LOT cheaper then in the store.  Will update on what I find out.