The gemara discusses the common problem of sirchas (strands that attach lobes of the lung to one another or to the rib cage) being an indication of a treifa. The gemara distinguishes between כסדרן and שלא כסדרן. Simply speaking כסדרן refers to an attachment of the lobes of the lungs that are adjacent to one another, which the gemara says is kosher because היינו רביתייהו, whereas an attachment between lobes that aren't adjacent -שלא כסדרן, renders that animal a treifa.
For background purposes, the lung has 4 lobes on the right side and 3 on the left. The very large lobe on the right and the left is called an אומא, and the upper ones (3 on the right and 2 on the left) are called אונא. Rashi and Tosafos both quote a major machlokes whether a sircha between two adjacent lobes are considered acceptable only in the אוני or even when there is an attachment between the אונא and the אומא. Additionally, there is a lobe in the center of the lung that is referred to as the עינוניתא דוורדא for it's rose like appearance - any sircha between that and another lobe of the lung is considered to be a problem.
Rashi in his explanation of this sugya clearly chooses the former of the two approaches that i mentioned in the previous blog. Rashi writes that the problem with a sircha is that it is indicative of a hole which is then filled up by the forming of a sircha. Rashi continues that even though it successfully covers the hole so that no air can penetrate, we pasken קרום שעלה מחמת מכה בריאה אינו כרום שסופו ליסתר. The last two words of Rashi - שסופו ליסתר, clearly indicate that the problem is that the closure will not hold, implying that if it were to hold such as surgical stitching, it would remove the problem of treifa. Regarding the distinction between כסדרן ושלא כסדרן which the gemara attributes to כסדרן being רביתייהו, rashi explains that adjacent lobes protect one another so that the sircha can strengthen rather than weaken. The entire approach of Rashi clearly implies that any fix that will actually hold is sufficient to remove the concern of treifa, even though the fix only came later and wasn't present from the beginning. Tosafos asks on Rashi, why would כסדרן be kasher, it should be no better than a krum that develops on an injury which doesn't fix the problem. Tosafos suggests that it could be that a sircha which attaches itself to another place (such as an adjacent lobe) has a tendency to strengthen and closes the hole better than a "krum" that is not attached to any other place. This further compliments the approach that a hole that renders that animal a treifa can be fixed, so long as it is strong enough to be maintained. Based on this, the Rashi 43a that we discussed in the previous blog would hold that if it is a permanent fix, the animal is no longer a treifa even if it develops later. But, rashi explains that even when the hole isn't truly plugged up, and is just being blocked by another organ, since it was there from the very beginning, this also allows that animal to be considered kasher and not a treifa.
Tosafos quotes Rabbeinu Chananel who takes the exact opposite approach to explain why a sircha is a problem. Rather than the sircha being an indicative of a preexisting hole, it is an indication that a hole is about to form. Tosafos points out that both the approach of rashi and rabbeinu chananel fail to explain why a hole can be tested by blowing into the lung while in a bucket of water. According to Rabbeinu chananel it will not bubble because the hole has not yet formed, and according to rashi it will not bubble because the sircha is blocking it from bubbling but is prone to fall off and therefore doesn't truly fix the hole.