Makhshirin, Chapter Six, Mishnah Five
This mishnah deals with sub-categories of the seven arch-categories found above in mishnah four.
1) Derivatives of water are: the liquids that come from the eye, from the ear, from the nose and from the mouth, and urine, whether of adults or of children, whether [its flow is] conscious or unconscious.
2) Derivatives of blood are: blood from the slaughtering of cattle and wild animals and birds that are clean, and blood from bloodletting for drinking.
3) Whey is like milk,
4) And the sap of olives is deemed like oil, since it is never free from oil, the words of Rabbi Shimon.
a) Rabbi Meir says: even though it contains no oil.
5) The blood of a sheretz is like its flesh, it causes uncleanness but does not cause susceptibility to uncleanness, and there is nothing else like it.
Section one: Various liquids emitted from the body are categorized as water.
Section two: The blood referred to in mishnah four is the blood that comes out of an animal when it is kosherly slaughtered. The mishnah adds that blood from bloodletting that he intends to give to another animal to drink also causes susceptibility. In all of these cases he wanted or needed the blood to come out of the animal or person. However, blood that simply comes out due to injury is not desirable and therefore does not cause susceptibility.
Section three: Whey, the milky substance left after making cheese, is considered to be like milk and does cause susceptibility.
Section four: The sap that comes out of olives causes susceptibility. Rabbi Shimon says that this is because we can be assured that there is some oil in it. Rabbi Meir says that even if we know that there is no oil in it, it still causes susceptibility because a person wants this sap to come out of his olives.
Section five: Blood of a sheretz causes impurity as does the flesh of the sheretz. However, it does not cause susceptibility to impurity. This means that if this blood falls on food that is not yet susceptible, the food remains pure.
The blood of a sheretz is unique in that it is the only blood that joins with the flesh to create the minimum measure that causes impurity. In other words, if there is a lentil’s worth of flesh and blood there is enough sheretz to cause impurity.