PERICARDIUM, PLEUROPERITONEUM, DIAPHRAGM AND MESENTERIES. 373 



In other words the septum comes to lie in an oblique cranio-caudal plane. The 

 pericardial cavity therefore comes to lie ventral to the ductus pleuro-pericardiaci. 

 The latter one on each side of the mesentery are two passages which com- 



Pericardial cavity 



Lateral mesocardium \ 



Pericardium 



Septum transversum 



Liver 



Ductus choledochus 



Yolk stalk - 



Ventral aortic trunk 

 Dorsal mesocardium 



Sinus venosus 

 Duct of Cuvier 



Left umbilical vein 

 Left omphalomes. vein 

 Ductus pleuro-pericardiacus 



tomach 

 Peritoneal cavity 



Pharynx s. R 



Dorsal mesocardium \ /, "c-w 



} C 





Ductus pleuro- 

 pericardiacus 



FIG. 330. From a model of the septum transversum, liver, etc., of a human embryo 

 of 3 mm. His, K oilman. 



municate on the one hand with the pericardial cavity and on the other hand with 

 the peritoneal cavity ,- while they themselves form the cavities into which the lungs 

 grow the pleural cavities. (Compare Figs. 330, 331 and 332.) 



Aorta 



Ductus pleuro- 

 pericardiacus 

 Duct of Cuvier 



Heart 



s> ^-- ^ Pericardial cavity 



FIG. 331. View (in perspective) of the pcricardial cavity and ductus pleuro-pericardiaci 

 of a rabbit embryo of 9 days. Ravn. 



The pleural cavities also become separated from the pericardial cavity, ap- 

 parently through the agency of the ducts of Cuvier. The anterior and posterior 

 cardinal veins on each side unite to form the duct of Cuvier which then extends 



