Midrash su Levitico 11:40

1) (Vayikra 11:29-31): "And this to you is what is unclean among the creeping things (sheratzim) which creep upon the earth: the weasel and the mouse, and the great lizard after its kind. And the gecko, and the land-crocodile, and the lizard, and the sand lizard, and the chameleon. These are what are unclean to you among all that creep." What is the intent of this? Because it is written (Vayikra 11:43): "Do not make yourselves tamei by them (sheratzim) and you will become tamei through them," I might think that inner-body tumah and the tumah of offerings are being spoken of; it is, therefore, written "And this (i.e., only this to you is what is unclean … the weasel and the mouse, and the great lizard, after its kind, etc." I might think that these confer tumah on men and implements and the others confer tumah on men but not on implements, or on implements but not on men; it is, therefore written (Vayikra 11:31): "These (are what are unclean to you"). Only these (confer tumah). Or, perhaps only these are excluded which are like the particular (kinds mentioned here, viz.:) Just as the particular have bones and reproduce, so, only those are excluded which have bones and reproduce. Whence do we derive (that also excluded are) those which have bones and do not reproduce or those which do not have bones and reproduce? From "These" are tamei to you among all that creep" — Only these among the sheratzim confer tumah.

7) I might think that the carrion of a beast would confer tumah upon one's clothes (if stuffed) into his esophagus (without his having touches or carried it, it being written (Vayikra 11:40) "And he who eats it shall wash his clothes"); it is, therefore, written (Vayikra 22:8) "Carcass or treifah he shall not eat to become tamei through it" — (We are speaking of that [a bird]) which confers tumah only through eating (and not through touching or carrying), excluding a beast, which confers tumah before it is eaten (by touching or carrying). I might think that bird carcass confers tumah according to Scripture, and beast carcass, a fortiori; it is, therefore, written "through it" — Through "it" (bird carcass) confers tumah in the esophagus, and not beast carcass. If so, why is it written (in reference to beast carcass, Vayikra 11:40) "And he who eats? To assign a (minimum) amount for (tumah of) touching and carrying — Just as for "eating," an olive-size, so, for "touching," an olive-size.