Click here for audio

מסכת חולין פרק ח משנה ה

Note:  Rennet is a combination of enzymes found in curdled milk in the stomachs of unweaned ruminants.  This substance enables the animals to digest their mothers' milk. and is used in the cheesemaking process to clot milk and form cheese curds.

קבת נכרי The rennet of [an animal slaughtered by] a gentile
ושל נבלה and of a neveilah (that is to say an animal slaughtered by a gentile is considered a neveilah)
הרי זו אסורה

is forbidden (as after death it is considered to be a part of the animal, which is a neveilah.  As is seen in the conclusion of this mishnah, this is not the final position of our tannah).

המעמיד One who sets [curdles milk]
בעור של קבה כשרה in a kosher stomach
אם יש בנותן טעם if it [the meat of the stomach] is sufficient to impart flavor
הרי זו אסורה it is prohibited.
כשרה שינקה מן הטריפה A kosher [animal] that suckled from a treifah,
קבתה אסורה its rennet is prohibited (as the milk of a treifah is prohibited even while it still lives)  .
טריפה שינקה מן הכשרה A treifah that suckled from a kosher [animal]
קבתה מותרת its rennet is permitted
מפני שהוא כנוס במעיה as it is gathered in its belly (i.e. it is considered separate and distinct from the animal.  This conclusion reflects the tanna's final position on the matter, which differs from the first part of the mishnah).

פרק ח משנה ו

חמר בחלב מבדם There is a stringency by chelev (certain prohibited animal fats) over blood,
וחמר בדם מבחלב and a stringency by blood over chelev,
שהחלב מועלין בו as one can transgress the prohibition of improperly benefiting from consecrated chelev (and will incur the penalties for both chelev and me'ilah)
וחיבין עליו

and one is liable (i.e. one is liable for the transgression of eating chelev in addition to the following transgressions) 

משום פגול for eating from a sacrifice slaughtered with the improper intent to eat it after its allotted time
ונותר וטמא and leftover [sacrificial meat after the time for it have been burnt on the altar has elapsed]; and [the transgression of consuming a sacrifice while] tamei,
מה שאין כן בדם which is not so by blood (in these cases one will only be liable for eating blood);
וחמר בדם and a stringency by blood,
שהדם נוהג as [the prohibition against consuming] blood is practiced
בבהמה וחיה ועוף by domestic animals, wild animals, and birds,
בין טמאים ובין טהורים whether kosher or non-kosher,
והחלב אינו נוהג and chelev is not practiced [prohibited]
אלא בבהמה טהורה בלבד but by kosher domestic animals alone.