Chullin 46: Smooth Lungs, Glatt Kosher

Today's daf teaches us about blemishes found in the lungs of an animal to be sacrificed.  If the lobes of the two lungs are stuck together by an adhesion, fibrous tissue, the lungs cannot be assessed to render the animal permissible (or not).  This is only the case when the lobes are not naturally beside each other, which is unusual. 

Steinsaltz teaches us that animal lungs contain four or five lobes: two at the bottom, three on the left side and two on the right side.  Commonly mucus will leak from one lobe to another and thicken another lobe.  

Rashi says that these adhesions are proof of a hole in the animal's lung that was covered by hardened mucus.  The hold shows that the animal is a tereifa. It is terminally ill and not kosher.  Tosafot argue that this is an ordinary occurrence and that the animal did not necessarily have a hole in its lung.  Once the adhesion breaks off, however, it will create a hole and thus the animal is a tereifa.  The rabbis discuss ways of finding holes in the lung, including filling them with water or air.

Glatt, smooth, describes a lung that has no adhesions and thus there is no guessing as to whether or not there is a blemish in the lung (stringently, all of these cases are called tereifot).  We still use the term glut kosher to describe stringent adherence to the laws regarding these issues.