What is “Glatt Kosher”?
On today’s daf we learn that Rava taught: If two lobes of the lungs adhere to each other by fibrous tissue, they cannot be checked to render the animal permitted. This is so, however, only if the lobes were not adjacent to one another, but if they were adjacent it is permitted, for this is their natural position.
A normal set of animal lungs contains a number of lobes – three on the left side and two on the right side – aside from the two larger lobes at the bottom. It is a common occurrence for viscous mucus to leak from one lobe and thicken on another one of the lobes.
There are two main approaches in the rishonim in explanation of these adhesions. According to Rashi, they are indicative of a hole in the lung of the animal that has been covered by hardened mucus, and the animal cannot be permitted because a hole in the lung indicates that the animal is a tereifa – it is terminally ill, and therefore not kosher. Tosafot argues that this is a normal occurrence and does not indicate that the animal had a hole in its lung. Nevertheless, when the adhesion breaks off it will cause a hole to be formed in the lung, and the animal is therefore viewed as already considered a tereifa. The Gemara’s ruling is that the animal’s lungs cannot be checked, that is, even if they are filled up with air to see whether there are holes, since we already know that there is either already a hole or there is bound to be one in the future, checking for a hole is moot.
According to the view of modern medicine, adhesions on the lungs stem from infections. The most common situation is when the animal suffers from infections in the chest membrane. When that occurs, the body secretes substances to build up the internal tissues. Appropriate care and avoidance of cold can significantly lower the incidence of such adhesions in animals.
The Shulḥan Arukh (Yoreh De’ah 39:4, 10, 13) rules that we do not distinguish between thick and thin adhesions – all are considered to be problematic and the animal is rendered a tereifa that cannot be checked. The term “Glatt” (smooth) refers to this ruling, since the animals lungs are required to be totally smooth. The Rema disagrees and suggests that thin adhesions can be squeezed or peeled off, after which the lungs can be checked for holes.