While discussing medical treatments, the Gemara also discusses the side-effects caused by some treatments that were common in those times.
The Gemara discussed the remedy for jaundice, saying that one should drink two of the ingredients mentioned together with beer, and one becomes sterile from it.
The Gemara asks: And is it permitted to cause sterility? Wasn’t it taught in a: From where is it derived that castration of a man is prohibited? The verse states: “Those whose testicles are bruised, or crushed, or torn, or cut, shall not be offered to the Lord, and you shall not do this in your land” (Vayikra 22:24), meaning that you shall not do it to yourselves; this is the statement of Rabbi Ḥanina. Apparently, it is prohibited to castrate a man.
The Gemara answers: This prohibition applies only in a case where one intends to castrate. Here, in the cure for jaundice, the sterility happens on its own, incidental to the treatment.
Proof is cited from that which Rabbi Yoḥanan said: One who seeks to castrate a rooster should remove its comb and it will become castrated on its own. Incidental castration is permitted. The Gemara rejects the proof. Didn’t Rav Ashi say: It is arrogance that it assumes when it has its comb, and when the comb is removed it becomes depressed and no longer procreates. However, it is not actually castrated. Rather, apparently this remedy for jaundice is permitted only for one who is castrated and for whom causing sterility is not a concern.
The verse quoted in the Gemara with regard to an animal with torn or cut testicles is referring to offering blemished animals as sacrifices. In that context, the Torah is referring only to the suitability of damaged animals for the altar. The end of the verse: “And you shall not do this in your land,” teaches that castration in any form is considered a blemish for an animal, and that it is prohibited to castrate an animal. This prohibition applies to all male animals, including those which cannot be offered as sacrifices. However, the Sages infer from the verse that any damage caused to the normal functioning of an animal’s reproductive system, even if caused indirectly, undermines God’s purpose in Creation, as the verse states, “He did not create it for naught; He formed it to be settled” (Yeshayahu 45:18). According to the Rambam, causing infertility in female animals violates a rabbinic prohibition.