Tosefta על כלים 1:5

And these are the tereifot (=טרפות, "mortal injuries or defects," lit. "torn flesh" (see Ex. 22:30)): A perforated gullet, a windpipe severed widthwise, behold this is disqualified. Rabbi Shimon ben Elazar says, in addition, [an animal] whose nerve tissue was "emptied" [from the spinal cord (Hul. 45b:17)] is disqualified. [An animal that had] a broken spine and a majority of its [spinal] cord was cut is disqualified. [An animal with] a withered lung, or if it no spinal cord is present, is disqualified. Rabbi Ya'akov says, even if it is perforated. If the liver is removed and there does not remain in it [a sufficient quantity of flesh] to allow a scab to form ("כדי להעלות ארוכה," see Kel. 1:5), it is disqualified. [An animal whose] inner stomach is perforated, or where the majority of the outer stomach is torn [is disqualified]. Rabbi Yehudah says, [a tear the size of] one handbreadth in a large [animal], and in a smaller [animal] if most of it [was torn], it is disqualified. And how large [must the stomach be for an animal to be deemed "large"]? Two handbreadths, behold, that is large. Less than that, behold, it is [a] small [animal]. What is the "inner stomach"? Ben Sheila, Head of the Seventy ("ראש שבעים," alt., "ראש טבחים" = "head butcher," see Minchat Yitzchak) testified in Tzippori in the name of Rabbi Nathan: It is the cecum (Hul. 50b:2).