TRANSVERSE SECTIONS OF A TEN MM. PIG EMBRYO 



133 



Stomach. On either side of the circular dorsal aorta are the mesonephroi, while dorso-laterally 

 are sympathetic ganglia. The pleural cavities now communicate freely on both sides with the 

 peritoneal cavity. A section of the lesser peritoneal sac appears as a crescent-shaped sUt at 

 the right of the esophagus. In the right dorsal lobe of the liver is located the inferior vena 

 cava. Near the median hne ventral to the lesser sac is the large ductus venosus. 



Section through the Stomach and Liver (Fig. 138). — Prominent in the body cav- 

 ity are the mesonephroi and liver lobes. The mesonephroi show sections of coiled tubules 

 lined with cuboidal epithelium. The glomeruli, or renal corpuscles, are median in position 

 and develop as knots of small arteries which grow into the ends of the tubules. The thickened 

 epithelium along the median and ventral surface of the mesonephros is the anlage .of the genital 

 The body wall is thin and hned with mesotheKum continuous with that which covers 



Spin il I I 



Notoclior I 



Dorsal aoiia 



Plica vend cava 

 Inferior vena cava 



Lesser omentum 



Spinal ganglion 



Base of upper limb 



Glomerulus of 

 mesonephros 



Greater omentum 

 Stomach 



Dorsal lobe of liver 

 Ductus venosus 



Ventral lobe of liver 



Ventral attachment of liver 



Fig. 138. — Transverse section through the stomach and liver of a 10 mm. pig embryo. X 22,5. 



the mesenteries and organs. The mesothelial layer becomes the epithelium of the adult peri- 

 toneum, mesenteries, and serous layer of the viscera. The stomach lies on the left side and is 

 attached dorsally by the greater omentum, ventrally to the liver by the lesser omentum. The 

 right dorsal lobe of the liver is attached dorsally to the right of the great omentum. In the 

 liver, ventral to this attachment, courses the inferior vena cava and the attachment forms the 

 plica vence cavcB. Between the attachments of the stomach and liver, and to the right of the 

 stomach, is the lesser peritoneal sac. In the liver to the left of the midline is the ductus 

 venosus, sectioned just at the point where it receives the left umbilical vein and a branch from 

 the portal vein. The ventral attachment of the liver later becomes the falciform ligament. 



Section through the Hepatic Diverticulum (Fig. 139). — The section passes through 

 the pyloric end of the stomach and duodenum near the attachment of the hepatic divertic- 



