Reference for Chullin 185:8

אמר ר' יוחנן

Abaye answered: An animal whilst alive has its limbs dislocated.<span class="x" onmousemove="('comment',' When the animal is in motion its limbs and muscles slip away from their normal positions and are temporarily dislocated. Consequently the fat under the loins is not always covered with flesh, and it is therefore forbidden.');">³</span>

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