The broad ligament extends across the convex cephalic surface of the liver uniting it to the ventral abdominal wall and diaphragm, while its free falciform edge apparently stops at the umbilical notch in the ventral border of the organ. Actually, however, the obliterated vein is surrounded in the bottom of the fissure, by a peritoneal fold which effects the junction between broad ligament and lesser omentum. We will see later in what way the permanent adult arrangement of the lesser omentum is brought about. For the present we can state, on the hand of the schematic Fig. 273, that the free caudal edge of the falciform ligament containing the umbilical vein, and the free edge of the gastro-hepatic omentum form together originally the caudal free edge of the ventral mesogastrium, which membrane becomes separated, by the growth of the liver, into suspensory or broad ligament and lesser or gastro-hepatic omentum. [Illustration: FIG. 275.--Abdominal viscera of _Iguana tuberculata_. (Columbia University Museum, No. 1313.)] This primitive disposition of the ventral mesogastrium and the viscera connected with the same, is well shown in some of the lower vertebrates in whom the development never proceeds beyond the early mammalian stages. Fig. 275 shows in profile view from the right side the situs viscerum and peritoneum in _Iguana tuberculata_.[5] The two dorsal aortic roots are seen to unite to form the main aorta, which descends between the layers of the dorsal mesentery, sending branches to the dorsal margin of oesophagus and stomach. From the opposite border of the stomach the ventral mesogastrium is derived. Its dorsal segment (gastro-hepatic omentum) connects liver and stomach, carrying between its layers the portal vessels, hepatic artery and biliary duct. The ventral segment of the membrane, forming the suspensory or broad ligament, extends between abdominal wall and ventral surface of the liver. Caudad, the lesser omentum and the suspensory ligament are seen to have a common concave falciform edge. [5] _Iguana tuberculata_, one of the large lizards native of South America. This animal forms an excellent object for the comparative study of the visceral and vascular anatomy of the abdomen. It possesses a well-differentiated intestinal tract, several coils of small intestine, a well-marked caecum and large intestine. The examination of this or a similar reptilian form is to be highly recommended. Iguana is easily obtained in any of our large cities, as a considerable number of these animals are annually imported from Mexico and the South American states. The ventral abdominal vein ascends between the layers of the suspensory ligament and near the liver becomes connected by a large branch with the portal vein. A few smaller branches are seen passing from the abdominal wall beyond this point. In this reptile, therefore, the permanent vascular arrangement corresponds to an early human embryonic stage.