1702 



1 1 r: MAN ANATOMY. 



Development of the Peritoneum. The attachment of the primitive ali- 

 mentary tube, from the oesophagus downward, to the posterior wall of the body- 

 cavity by means of a sagittal fold, the primary mesentery, has already been noted 

 (page 1697). Likewise the conventional division of this duplicature into a lower part 

 attached to the intestines, the mesenterium commune, and an upper portion passing to 

 the dorsal surface of the stomach, the mesogastrium. The latter differs from the 

 common mesentery in not ending at the ventral border of the digestive tube, but, 

 after enclosing the stomach and the upper part of the duodenum, in continuing for- 

 ward, embracing the liver, to be attached to the ventral body-wall. The portion of 

 the duplicature between the stomach and duodenum and parietes is known as the 

 ventral mesogastrium, or anterior mesentery, as distinguished from the dorsal meso- 

 gastrium behind the stomach. The ventral mesentery is at first attached above to 

 the septum transversum and in front to the body-wall as far as the entrance of the 

 umbilical vein, which occupies its lower free border as far as the liver. As already 



FIG. 1437. 



Truncus arteriosus 



Ventricle 



Diaphragm 



Liver 



Stomach 



.Omental sac 

 Greater omentum 



Vertebral column 



Spinal cord 



Lu 

 Pleural sac- 



Communication 



between pleu- rJ3 

 ral and perito- i 

 neal cavities 

 Spleen 



Sexual gland \ Vff; 

 Kidney 



Atrophic Wolffian body 



Part of sagittal section of pig embryo of 23 mm., showing thoracic and abdominal organs. X 15- 



noted incidentally, the latter organ during its development is almost entirely freed 

 from the diaphragm by the appearance of grooves on each side and before which 

 cleave the septum transversum and almost completely separate the lower layer con- 

 taining tin liver, the lateral expansion of which organ materially aids in this process 

 of delamination. The separation, however, is not complete, since the recesses over 

 tin- >ides and top of the liver do not quite meet in the mid-line, but leave a sagittal 

 fold attached above to the diaphragm and below to the supero-ventral surface of the 

 liver, beyond which it extends along the body-wall as far as the umbilicus. It is 

 evident that this primitive, sickle-shaped fold foreshadows the persistent falciform or 

 susfr-nsun- /i^nnifn/ of the adult origin, the lower free border of the duplicature en- 

 do-Mii- tlie umbilical vein, later the ligamentum teres, in its passage to the under 

 surface of the liver. The portion of the sagittal fold continued from the liver to the 

 digestive tube later constitutes {\\(.-^ctstn'-/n'f)aticorlesseroinf?itni and contains the 

 bile-duct, portal vein, and hepatic artery. 



