|layer of fat...|
This is particularly the layer of fat that covers the animal's two stomachs, the omasum (hemses) and the reticulum (beth ha-kosoth) (Chullin 93a; Yad, Maakhaloth Assuroth 7:6; Yoreh Deah 64:8). Some also include the fat on the paunch or rumen (keres) (Tosefta, Chullin 9:3; Hagahoth Maimonioth, Maachaloth Assuroth 7:6; Yoreh Deah 64:9). This is often identified as the viscal peritoneum.
Specifically not included, however, is the fat attached to the abdominal cavity (Sifra). Also not included is the fat on the intestines (Yad, Maachaloth Assuroth 7:9; see next note 'all the other fat...'. See note on Leviticus 3:17.
|all the other fat...|
This, specifically, is the fat on the maw (keva) (Chullin 49b; Yad, Maakhaloth Assuroth 7:6; Yoreh Deah 64:14). This is usually identified with the grain-like protrusions of peritoneal fat now designated as appendices epiploicae (chitte de-karkashta; Chullin 49b). Some authorities also include the fat on the intestines (Rabbi Akiba, Chullin 49b). The fat on the spleen is also included (Chullin 93a; Yoreh Deah 64:10). This includes fat that is actually attached to these organs (Ralbag).