THE RABBIT. 307 



the diaphragm, the third near the point at which the 

 postcaval enters the liver. 



221. The posterior phrenic veins (i.ph) taking the blood from the 

 abdominal surface of the diaphragm to the postcaval. 



XXIV. Cut away enough of the ribs on one or both 

 sides to get a good view of the interior of the 

 thorax, and make out : 



222. The relations of the pleurae : the outer or parietal 

 layer of each lines its own half of the thorax, to the walls of 

 which it adheres closely ( 161) : the adjacent or inner faces 

 of the two parietal layers form a double median vertical 

 partition, the mediastinum : the mediastinal space 

 included between the two layers of this partition is largely 

 occupied by the heart and its surrounding pericardium, and is 

 thus practically obliterated in the greater part of its extent : it 

 is, however, readily made out in the interval between the heart 

 and the sternum, where it is called the ventral (anterior) 

 mediastinai space : at the entrance of the bronchi each 

 pleura is reflected over the corresponding lung, forming the 

 thin, closely adherent visceral layer. 



XXV. Cut through the posterior end of the sternum : 

 separate the mediastinum from the dorsal surface 



, of the bone and turn it forwards : open the 

 pericardium by a longitudinal incision, and make 

 out : 



223. The relations of the pericardium: its outer or 

 parietal layer forms a loose bag investing the heart, and, 

 at the origins of the great vessels ( 229-232 and 237), 

 reflected on to the surface of the heart, forming the thin, 

 closely adherent visceral layer : in the space included 

 between the two layers is contained a small quantity of 

 colourless pericardial fluid. 



