What meat does McDonald's use?

McDonald's burger patties are made from 100% beef. Its like you buy 75% or 80% lean ground beef, put it through a machine which flattens it into the patty shapes. The patties are labeled 10:1 which is the weight (ten patties to a pound) or "reggy" and 4:1 (four patties to a pound) or "1/4 pounder". The beef is then seasoned with pre-mixed seasoning which is 87% salt and 13% pepper. The beef is good, i would like to know what those damned mcnuggets are made of, or the McChicken. Hmmmmm :/