THE RABBIT. 311 



232. The thoracic portion of the postcaval vein {ptc), 

 passing forwards from the diaphragm to the right auricle. 



233. The anterior phrenic vein {a.ph), passing forwards from the 

 diaphragm, alongside the postcaval, and pouring its contents into the 

 right precaval. 



234. The oesophagus, or gullet, passing from the 

 anterior boundary of the thorax, dorsal to the trachea and 

 between the lungs, backwards to its aperture in the 

 diaphragm. 



235. The paired phrenic nerves, passing from the 

 anterior boundary of the thorax backwards to the diaphragm, 

 which they supply : the right nerve runs alongside the right 

 precaval, across the right auricle and along the postcaval, 

 the left nerve runs along the left precaval and then passes 

 just internal to the left lung. 



Traced forwards, the phrenic is found to take its origin from the sixth 

 cervical nerve : if followed beyond the thorax, it should be left until the 

 nerves of the neck (§§ 244-246) are dissected. 



236. The thoracic portions of the vagi {see § 186 and 244) : the right 

 vagus enters the thorax to the right of the trachea along which it runs, 

 thence passing on to the gullet and so through the diaphragm to the 

 stomach : the left nerve runs at first parallel to the left precaval, 

 finally also reaching the gullet, along which both nerves take a spiral 

 course. 



237. The aorta {ao), a large, elastic, thick-walled vessel, 

 of a whitish colour, proceeding from the base of the heart 

 behind the pulmonary artery ; it rises clear of the heart, then 

 bends over to the left side, forming the arch of the 

 aorta (a.ao), and passes backwards, arching over the left 

 bronchus (§ 228) to reach the ventral face of the spinal 

 column, along which it passes as the dorsal aorta [d.ao) 

 throughout the whole length of the thorax and abdomen, 

 dividing at last into the two common iliac arteries 



