Debate Responses
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It’s important to note that murex blood can’t be called reir (mucus/slime), because reir specifically refers to something that drips. As Rashi explains on Shmuel I (21:14), on the verse “and his reir went down to his beard”: “Reir — his saliva, something that drips is called reir,” and likewise in the phrase reir chalamos (Iyov 6:6) and rar besaro (Vayikra 15:2), end quote.
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ומשנים הריר עד שיהא דומה ממש לקלא אילן
The process involves altering the secretion (rir) so that it appears just like Kala Ilan
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It seems he used this wording in order to raise a question — namely, that the Gemara refers to “dam chilazon” (blood of the chilazon), while the fluid secreted by the Murex is not technically blood (at least based on what we currently know). However, it is not clear whether this secretion doesn’t in fact originate from the blood, perhaps having thickened into a mucous-like form. But in any case, this isn’t a strong question. We find that even other bodily fluids are sometimes referred to as “blood.” For example, in Nidda (41:2 “אמר רבי יוחנן מקור שהזיע כשתי טיפי מרגליות” ), Rabbi Yochanan says about tipin shel margoliyos (pearlescent drops), “they are white and clear blood,” and Rashi there explains that phrase as “white, clear blood.” Likewise, the Rambam (Rambam Hilchos Klei HaMikdash – the vessels of the Temple 1:3 ) refers to mor (myrrh) as “blood,” even though it’s not actual blood.
In fact, we find in common language that the secretion of the Murex was referred to as “blood” by Yosefon (Antiquities 3:7:7). And if the Torah speaks in human terms, then all the more so Chazal did as well.
One might still ask: if so, what was Tosafos’ question in Shabbos 75a (s.v. keiheichi)? They write: “It is difficult for R’ Yitzchak — after all, the extraction of blood should be considered taking a life.” But if the fluid isn’t animal blood, then what is the problem?
It would seem that this is exactly what Tosafos answer: “Rabeinu Tam replied that the blood used for dyeing is mifkad pakid (loosely contained and not absorbed), and one is not liable for that blood.” Meaning: the dam techeiles isn’t the kind of blood that causes liability for taking a life — rather, it’s a different type of bodily fluid, which is still called “blood” in the Gemara.
Nor can one object and say this isn’t definitive — that perhaps even animal blood can be mifkad pakid, and that Tosafos must have been assuming it was real blood, otherwise their question wouldn’t make sense, and maybe in their answer they changed that premise. But this isn’t correct. If you look closely at their language, they write: “Only that which is fit for dyeing is mifkad pakid,” which implies that other types of blood are not fit for dyeing. Only this particular type — the one that’s mifkad pakid — is fit for that use. That means we must say it’s a different substance entirely from standard blood.
Additionally, it’s not accurate to refer to the secretion as reir (slime), because reir specifically refers to something that drips. As Rashi explains on the pasuk in Shmuel I (21:14), “And his reir ran down his beard”: “His spit — something that drips is called reir.” And he gives other examples too, such as reir chalamos in Iyov 6:6 and rar besaro in Vayikra 15:3.
