Reference for Chullin 100:25
אמרי במערבא משמיה דרבי יוסי בר חנינא
R'JUDAH SAYS, IN A LARGE ANIMAL etc. R'Benjamin B'Japhet reported in the name of R'Eleazar, LARGE does not mean a large animal nor SMALL a small one, but the meaning is: If it was torn to the extent of a handbreadth but this was not the greater portion [of the rumen, it is trefah], and this is what the Mishnah teaches us by stating IN A LARGE ANIMAL TO THE EXTENT OF A HANDBREADTH; and if the greater portion was torn but it was not the extent of a handbreadth, [it is trefah], and this is what the Mishnah teaches us by stating IN A SMALL ANIMAL THE GREATER PORTION OF IT.<span class="x" onmousemove="('comment',' Either the one measure or the other measure, whichever is the smaller, will render the animal trefah.');"><sup>11</sup></span>