BODY CAVITIES, DIAPHRAGM AND MESENTERIES 201 



Soon dorsal prolongations of the lateral liver lobes, the coronary appendages 

 come into relation with the septum dorsally and laterally. The attachment of 

 the liver to the septum transversum now has the form of a crescent, the dorsal 

 horns of which are the coronary appendages (Fig. 193). This attachment be- 

 comes the coronary ligament of the adult liver. The dorso-ventral extent of the 

 coronary ligament is reduced during development and its lateral extensions upon 

 the diaphragm give rise to the triangular ligaments of each side. 



The right lobe of the liver, as we have seen, comes into relation along its 

 dorsal surface with the plica vena cava in 9 mm. embryos (Figs. 192 and 193). 

 This attachment extends the coronary ligament caudally on the right side and 

 makes possible the connection between the veins of the liver and mesonephros 

 through which the inferior vena cava is in part developed. The portion of the 

 liver included between the plica vena cava and the lesser omentum is the cau- 

 date lobe (of Spigelius). 



In a fetus of five months the triangular ligaments mark the position of the 

 lateral coronary appendages. The umbilical vein courses in a deep groove along 

 the ventral surface of the liver and with the vena porta and gall-bladder bounds 

 the quadrate lobe. 



Changes in the Dorsal Mesentery. — That part of the digestive canal which 

 lies within the peritoneal cavity is suspended by the dorsal mesentery which at first 

 forms a simple attachment extending in the median sagittal plane between body 

 wall and primitive gut. That portion of it connected with the stomach forms 

 the greater omentum, the differentiation of which has been described (p. 199). 

 The mesentery of the intestine is carried out into the umbilical cord between the 

 limbs of the intestinal loop. When the intestine elongates and its loop rotates, 

 the caecal end of the large intestine comes to lie cranially and to the left, the small 

 intestine caudally and to the right, the future duodenum and colon crossing in 

 close proximity to each other (Fig. 196 A). On the return of the intestinal loop 

 into the abdomen from the umbilical cord the csecal end of the colon lies to the 

 right and the transverse colon crosses the duodenum ventrally and cranially. 

 The primary loops of the small intestine lie caudal and to the left of the ascending 

 colon (Fig. 196 B) . There has thus been a torsion of the mesentery about the base 

 of the superior mesenteric artery as an axis. From this focal point the mesen- 

 tery of the small intestine and colon spreads out fan-like. The mesoduodenum is 

 pressed against the dorsal body wall, fuses with its peritoneal layer and is obliter- 

 ated (Fig. 195). Where the mesentery of the transverse colon crosses the duo- 

 denum it fuses at its base with the surface of the latter and of the pancreas. Its 



