Reference for Chullin 35:38
דיקא נמי דקתני ב"ש פוסלין וב"ה מכשירין ולא קתני ב"ש אוסרין וב"ה מתירין וליטעמיך ליתני
Howbeit, R'Jose son of R'Judah said this only with regard to the top ring, since [the cartilage] surrounds the windpipe entirely, but he did not say this with regard to the other rings.<span class="x" onmousemove="('comment',' Which do not completely surround the windpipe but are connected by a mucous substance. These rings, therefore, being incomplete, are not regarded as the proper place for slaughtering. Accordingly Rab and Samuel hold that the slaughtering can only be performed by cutting either in the top ring or between the other rings. This is Rashi's interpretation. There are other interpretations suggested by Rashi and Tosaf. q.v.');"><sup>15</sup></span>