In this article we will clarify the meaning of a sircha and how it impacts the kashrut of an animal. A sircha is a thin membrane that is attached to the lobes of the lung as can be seen in the diagram above.
Two critical questions need to be answered when dealing with sirchot on the lungs. Firstly, what is the cause of sirchot, and how are they formed? Secondly, what impact does this have on the actual lung from a halachic perspective?
How is the Sircha Formed?
The Gemara in Masechet Brachot states:
תנו רבנן: כליות יועצות, לב מבין, לשון מחתך, פה גומר, ושט מכניס ומוציא כל מיני מאכל, קנה מוציא קול, ריאה שואבת כל מיני משקין…
“The Sages taught in a baraita with regard to the roles of various organs: The kidneys advise, the heart understands, the tongue shapes the sounds that emerges from the mouth, the mouth completes the shaping of the voice, the esophagus takes in and lets out all kinds of food, the trachea produces the voice, and the lungs draw all kinds of liquids…”
The Gemara here is praising the human body in the manner of the pasuk, “mibsari echzeh Eloka,” “from my flesh I shall see G-d,” and in that context it explains the function of each organ in the body. The lung, which helps a person breathe, is described as drawing in all types of liquids. This seems strange though, as the lung absorbs air and not liquid, and the Sages even warn us not to speak while eating lest the trachea precede the esophagus (and cause the person to choke). It is clear that Chazal understood the anatomy and the function of the lung and it was not meant to absorb liquids but air. Although one could argue that the Gemara here should not be taken literally (as seem clear regarding the line about the kidneys advising) but is speaking on a mystical level. Nevertheless, at least some Rishonim understood that some of the descriptions are to be taken literally, including the description about the lungs.
Rashi explains the Gemara as follows: “Although they (the liquids) enter the body through the stomach via the esophagus, the lung draws it out from the walls of the stomach.” This explanation of Rashi also seems strange, as how and why would these liquids go from the stomach, which is lower down in the body of the animal, back up to the lungs? Moreover, modern science is not familiar with any anatomic passageway from the stomach to the lungs. Finally, why is this something that Chazal find praiseworthy?
The sefer Sichat Chullin explains Rashi in the following manner: “There are veins and the like connecting the liver and the lungs. Through these veins, liquid or moisture is transferred in an indirect manner. Perhaps one can understand that this moisture has a very important function, as it keeps the external part of the lungs soft and hydrated, as anyone who has felt the lungs knows how important this is. If the lungs are not kept hydrated, the animal could not survive and would become a tereifa. However, sometimes there is too much moisture and it actually penetrates the lungs. After a perforation is made, this liquid congeals and forms a membrane called a sircha.”
Another understanding is based on the Ma’adanei Yom tov. He explains that these liquids enter the lungs via the air that the animal breathes (see diagram below). Since there is moisture in the air, this moisture gets trapped in the lungs. Accordingly, the perforation of the lungs occurs from the inside out as these liquids break through the walls of the lungs. These perforations are then closed up by the congealed liquid (fibrin – the protein form of liquid that causes the adhesions), thereby forming a sircha. As opposed to the first explanation that the liquids enter the lungs from other parts of the body, the Ma’adanei Yom Tov understands that these liquids go directly to the lungs and then puncture the lungs.
A third explanation is brought by Rav Dr. Yisrael Levinger in his sefer Tereifot B’yisrael that could in fact be compatible with the first two explanations as well. Rav Levinger did a survey of different types of animals to determine the reason for sirchot in the lungs. His findings were as follows: Since calves raised in farms today are weaned from their mother’s milk earlier than in nature, this causes a weakening of their immune system and a predisposition to getting an infection of the lungs. These bouts of infections are more common when calves are more exposed to the elements. This immune weakness does not appear in calves that are left to wean naturally in a more gradual manner. According to Rav Levinger, the main cause of sirchot is due to an infection of the lungs due to contagious pneumonia. But perhaps this explanation of Rav Levinger can in fact also explain the opinion of the Ma’adanei Yom Tov, as the liquid that enters the lungs from the air may also contain the pneumonia particles. Even according to Rashi, one can explain that due to the low immune system and decrease in health of the lung, it is more easily penetrated from the outside.
It should be noted that Chazal felt that these sirchot were significant in terms of being an indication of the deterioration of the animal’s health (which is supported by Rav Levinger’s survey), whereas the Greek philosophers did not attach any such significance to these sirchot.
What is the Significance of the Sircha?
The Mishna in Masechet Chullin states: “These are tereifot within an animal… A lung that was punctured…” It seems from here that the actual hole in the lung is what renders the animal a tereifa. However, the sircha is of critical importance as it gives an indication that the lung has in fact been punctured. There is a fundamental argument between Rashi and Tosafot as to how the sircha gives this indication. Rashi claims that there is no such thing as a sircha without the lung having been punctured; meaning that under every sircha, there is de facto a puncture. Tosafot question Rashi’s assertion based on the fact that we do find certain sirchot mentioned in the Talmud that do not render an animal into a treifa, even though the halacha is that any puncture in the lung would make the animal a tereifa.
Tosafot offer two explanations for Rashi. A) Even according to Rashi, one must explain that there are certain sirchot that were not formed due to a perforation, but are just the result of rir, some type of mucus. These sirchot would not render the animal to be a treifa even according to Rashi. B) Although every sircha does indicate that there was a perforation of the lung, certain sirchot have been able to close the perforation to such an extent that the animal is able to continue breathing normally, and we are not concerned that the sircha will break and the perforation will open up again. Accordingly, only a sircha that does not close the perforation in a complete and secure manner would render the animal a tereifa.
In addition to explaining Rashi, Tosafot also offer their own explanation as to what a sircha indicates and its halachic ramification. They state: “That a sircha forms on any part of the surface of the lung without there being a perforation, for the lungs absorb all types of liquid (see diagram above), and what makes it into a tereifa… is due to the fact that in the end, the sircha will tear apart (forming a perforation) and since this will eventually happen, we already view it as if it had torn open.”
According to Tosafot, the concern is that as the animal grows and moves, and with each breath the lung expands and contracts, pressure is exerted on the sircha, which will eventually tear and perforate the lung. This is similar to one who stretches an elastic band repeatedly. At some point, the elastic band will snap. So too, when the sircha tears, it will remove some flesh from the lung and hence cause the perforation (see diagram).
The Rosh paskens in accordance with Rashi, while the Ran accepts the opinion of Tosafot. The Ran writes that there are a few halachic ramifications between the two explanations of Rashi and Tosafot, but the truth is that it is difficult to arrive at concrete conclusions based on the different opinions.
Perhaps this is why the Shulchan Aruch did not decide which explanation is the correct one, as it is difficult to find an absolute nafka mina between the opinions. The Acharonim as a general rule always cite both explanations when explaining the halachic significance of sirchot. However, Rav Levinger offers a new perspective in explaining this argument:
“What is accepted in the veterinary world is some middle ground between these opinions. The sircha appears in the lung as a result of an infection of the lungs. At the time of the infection the membrane becomes penetrable, and liquids escape from it in order to form a new layer which is stronger. This causes a new thin membrane which is formed on the outside of the lung.”
Based on this medical explanation, perhaps we can explain that Rashi, who understood that a sircha always indicates the presence of a perforation, was focusing on the fact that due to infection, the membrane is penetrated by the liquids, thus causing a perforation through which the liquids escape. But Tosafot, on the other hand, do not view the perforation of the original membrane as having any halachic significance, since it is quickly replaced by the new layer. Therefore, Tosafot maintains that a sircha is problematic only due to what may occur at a later stage.
Perhaps one can compare this argument to the dispute between Rabbi Yosei and the Chachamim regarding the lechem hapanim (the showbread). The Chachamim hold that one group of Kohanim remove the old bread while the other group immediately replaces the new bread, to the point that there was never a moment where the table remained empty. This was necessary in order to fulfill the requirement of it being “tamid.” Rabbi Yosei argues that the Kohanim first remove the old bread and only later is the new bread placed. In his view, this is also considered “tamid,” for the few moments that the table remains empty are insignificant.
Thus, the opinion of Rashi, that even a temporary perforation of the original membrane (before the new one develops) is significant and renders the animal a tereifa, is similar to that of the Chachamim that tamid is violated even for a short time. The approach of Tosafot that even if the thickness of the wall of the lungs is compromised for a few moments it is not considered nikva hare’ia – the lung being punctured (since this is a natural way for the body to heal itself) may be more similar to that of Rabbi Yosei, that even a short lapse in between the two breads still qualifies as tamid.
We hopefully now have a better understanding of the fundamental argument between Rashi and Tosafot as to how these sirchot are formed. Although often such a machloket Rishonim will be resolved one way or the other by the later poskim, in our case the Acharonim consider both explanations when trying to decipher the halacha in cases where it might hinge on one explanation or the other.
 Berachot 61b
 Iyov 19:26
 Ta’anit 5b; see also Pesachim 108a
 Rashi, Berachot 61b, s.v. sho’evet
 Sichat Chullin, p.210
 Ma’adanei Yom Tov on the Rosh, Chullin 3:14:80
 Rav Levinger is the rabbi of the city Munich, Germany, and author of the sefer Ma’or L’chullin and Tereifot B’yisrael.
 Tereifot B’Yisrael, p.63
 A mother’s milk contains important antibodies that help the body fight infections. When the calf is weaned too early, the immune system does not develop in the best way possible. It is noteworthy to mention the words of the Chazon Ish (O.C 48), who claims that it is considered pikuach nefesh regarding replacing a mother’s milk with formula.
 Encyclopedia Assia, volume 6, p.219
 Chullin 42b
 Rashi, Chullin 46b, s.v. leit lehu
 Tosafot, ibid.
 Rosh, Chullin 3:14
Ran, Chullin 11b in the pages of the Rif
 Menachot 98b