Reference for Bekhorot 40:24

אלא איפוך

Add the minority of miscarriages to the half which bear females, then males are in the minority and we do not take into consideration a minority? - Rather, reverse [the names above].<span class="x" onmousemove="('comment',' So that it is R. Joshua who maintains that a discharge exempts, and the same applies to the giving of milk, whereas R. Akiba only exempts where it is definitely known that it had given birth, but when it is not known, even if it discharges or gives milk, it is a doubtful first-born.');">¹³</span>

Jastrow

Jastrow