PERICARDIUM, PLEUROPERITONEUM, DIAPHRAGM AND MESENTERIES. 375 



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 



Stomach 

 Peritoneal cavity 



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

 of 3 mm. His, Kollman. 



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.) 



Pharynx s^^fj ^ \- 

 Dorsal mesocardium ^ / ; v ;■■ .^-y , „ - 



Ductus pleuro- 

 pericardiacus f 



Aorta 



Ductus pleuro- 

 pericardiacus 

 Duct of Cuvier 



■Heart 



^m^^^ Pericardial cavity 



Fig. 331.— View (in perspective) of the pericardial 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 



