Yosef Karo, Shulchan Aruch — 59 A beast that was skinned alive
“ Contains two Seif.1 Large cattle are forbidden. That's when it was skinned whether by man or by illness - it's treif. But if there remains of the hide the width of a Sela [sela coin, approx. 1/2 oz.] along the whole spine surface, a sela width on the navel, and a sela width at the head of the limbs, behold it's permitted (Rambam, Rashba, Ran and most poskim) . And if approximately a sela width is missing from the spine surface or off the navel or off the heads of the limbs, but the rest is there - it's kosher.Rema: But if it's missing from all those three and the rest is there - it's treif. ”
