(_b_) Distal caudal portion of the lesser omentum is twisted laterally and turned to the right by the change in the position of the stomach and the development of the structures connected with the liver at the transverse fissure. It is reflected from this fissure to the distal part of the lesser curvature and to the first portion of the duodenum. This transverse segment of the lesser omentum is a secondary derivative from the right leaf of the primitive membrane, produced by the enlarged area for entrance of umbilical and portal veins at the transverse fissure. It lies ventrad of caudal border of Spigelian lobe. 2. The distal segment of the original omentum containing the umbilical vein (round ligament), continues imbedded in the umbilical fissure, to the ventral margin of the liver, where it joins the layers of the suspensory ligament passing over the cephalic surface. 3. The adult lesser omentum at the transverse fissure may be regarded as a diverticulum of the right leaf of the primitive embryonal sagittal omentum. With the reduction of the umbilical vein after birth to form the round ligament this structure becomes deeply buried in the umbilical fissure. The ventral and dorsal layers of the lesser omentum at the transverse fissure thus become continuous with respectively the left and right layers of the second segment of the omentum which ascends vertically along the fissure for the ductus venosus. 4. The cephalic layer of the coronary ligament (Fig. 280) remains practically in the embryonic condition. The adult convex cephalic surface of the liver is traversed in the sagittal direction by the suspensory ligament which connects it with the abdominal surface of the diaphragm, and thus effects the division into right and left lobes on the convex surface. Arrived at the dorsal border of this surface (junction of "superior" and "posterior" surfaces) the right and left leaves of the falciform ligament turn at right angles into the cephalic layer of the right and left coronary ligament, which at each extremity meet the right and left caudal layers to form the triangular ligaments. It will thus be seen that the apparent irregularity in the relative arrangement of the s. c. "upper" and "lower" layers of the coronary ligaments, produced by the Spigelian recess, is only a difference in the interval between the two layers, caused by the vertical extent of the non-peritoneal direct diaphragmatic attachment of the right lobe to the right of the vena cava. =Comparative Anatomy of Spigelian Lobe and Vena Cava in the Cat.=--The lines of peritoneal reflection in the _cat's_ liver and the arrangement of the Spigelian lobe and recess are seen in Fig. 281, taken from a preparation hardened in situ. [Illustration: FIG. 281.--Liver of cat, hardened _in situ_. (Columbia University Museum, No. 1836.)]