Chullin 50: Comparing Perforations

When one finds a perforation in an animal, what are the protocols?  The rabbis describe a number of tests used to determine where the hole came from and whether it causes the animal to be a tereifa.  If the hole is on an animal's lung, a similar hole can be created to compare the two.  If the second hole looks like the first, then the first is determined to have been caused after the slaughter, and the animal is permitted.

Rava suggests that this comparison can be made on one but not both lungs.  The Gemara disagrees.  The rabbis decide that small animals can be compared and large animals can be compared but that small and large animals cannot be compared to each other.  Rashi asserts that comparisons between two different animals are never reliable.  He suggests that we are only to compare the small and larger lobes of the lungs.

The Rema (Shulchan Aruch Yoreh De'a 36:5) teaches that we cannot be experts in this method any longer.  There is no tradition that we can rely upon to test whether or not an animal is permitted.