Reference for Chullin 56:41
חצי אחד בעוף וכו':
When you turn to one part you must regard it as the greater portion [and therefore unclean], and when you turn to the other part you must regard it as the greater portion [and therefore also unclean]? - R'Papa answered: There cannot be two greater portions in one vessel!<span class="x" onmousemove="('comment',' In this case therefore, since each half must clearly be treated on the same footing, each must be considered as a half and no more, with the result that each half is clean. In the case of shechitah however, the two parts of the organ are not treated on the same footing, for we are only concerned with the part that is cut; hence we may regard the exact half which is cut as equivalent to the greater portion, with the result that the slaughtering is valid.');"><sup>14</sup></span>