Midrash for Chullin 99:33

אמר מר הלכה כרשב"ג בטרפה

Raba said: This is allowed only in the same lung, but we may not compare the defect in one lung with the defect in the other lung.<span class="x" onmousemove="('comment',' I.e., even in the lungs of one animal one may not compare a defect in the right lung with a defect in the left lung, or vice versa.');">¹⁶</span>

Sifrei Devarim