So it's 100% beef? - that's ok surely?
It used to be all lips, nostrils and bumholes, 8dave* - still 100% beef lips, nostrils and bumholes, though. I don't know if things have changed, but any meat product can be included, and this means eyeball, skin, veins - if it grows on a cow, it's 100% beef by the standards of the industry.
I'm pretty sure they stopped using brain tissue and spinal cords when the BSE scare hit the headlines, but as I understand it, everything else is valuable protein as far as the fast-food industry is concerned.
There is also a lot of corn syrup in even savoury dishes, apparently. This is both addictive and unhealthy. I know that food standards have tightened up a lot, so this may have been reduced.
It's largely mechanically-recovered meat - gristle etc - which is washed off the bones using high pressure hoses, shovelled up, chopped and shredded, coloured and chemically-flavoured, and shaped into meat-like stuff. Or used to be - as I say, it may have changed since I watched a vomit-inducing documentary a few years ago.
Still smells and tastes nice, though, even when I know what goes on behind the scenes . . .