Reference for Niddah 64:1

למעוטי איש מאודם

— To exclude a man from the uncleanness of a red discharge.<span class="x" onmousemove="('comment',' Of semen (v. infra) which is similar in nature to the discharge dealt with in the text under discussion. Only a woman's is subject to uncleanness but not that of a man. ');">¹</span>

Jastrow