Reference for Chullin 190:10

וכי מכללא מאי

Indeed you may be certain of this from his reply: 'The forbidden ones are more frequently found [here]'.<span class="x" onmousemove="('comment',' Which can only be explained by the fact that the place was frequented mostly by gentiles. In other districts, however, both heads might have been permitted, even though they had been out of sight for some time. Thus Rab's principle cannot be definitely inferred from this incident.');">⁴</span>

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