THE POSTERIOR VENA CAVA. 705 



Vena Portae (Figs. ;S89, 890). 



The manner in which this vessel comports itself jsjives it an altogether 

 peculiar physiognomy, and has caused it to be considered as a separate vascular 

 system.^ After what has been already said concerning the structure of the 

 liver, it must be admitted that the vena port* is distributed in that gland 

 exactly like an artery. 



It begins in the sublumbar region, at the anterior mesenteric artery, by the 

 union of three large radicles ; it is then directed forwards and a little to the 

 right, traversing the pancreatic ring, below the vena cava, and is afterwards 

 lodged in the great posterior fissure of the liver, where it ramifies l)y forming 

 the interlobular veins, the capillary divisions of which give rise to the suljlobular 

 vessels. 



Interlobular and suhlobular veins (Fig. 303, VP, Yh). These vessels having 

 been already studied in the description of the liver, we need not again occupy 

 ourselves with them, but refer only to a peculiarity incompletely noticed in that 

 description, with reference to the sublobular veins. 



We know that these vessels are divided into two categories, according to 

 the arrangement of their openings. The majority enter the vena cava in 

 forming a single confluent placed at the anterior extremity of the fissure in 

 the liver, at the phrenic veins ; the others open separately over the whole 

 extent of the hepatic portion of the venous trunk. In carefully examining 

 the confluent towards which all the veins of the first group converge, we 

 recognize the junction of three principal veins, one coming from each of the 

 hepatic lobes, and furnished with three very isolated, incomplete valves. With 

 regard to the vessels of the second group, Claude Bernard^ considers them 

 to come, for the most part, directly from the sublobular veins, and not from 

 the capillary network formed by these veins in the lobules of the liver. It is 

 true that injections readily penetrate from the vena portte into the vena cava, 

 but they do this quite as much by passing along the large sublobular vessels 

 as the canals of which we now speak ; and, besides, if the material forced into 

 the vena portae is mixed with some imperfectly powdered colouring matter, 

 the injection will arrive colourless, or but slightly tinged, in the sublobular 

 vessels and the vena cava. These facts, we see, do not militate in favour of 



' Nevertheless, tliere are communications between the portal system and the general 

 circulation, throngh the nieriiura of the cesophageiil and haMuorrhoidiil veins. These com- 

 munications become very evident when the circulation in tlie liver is obstructed. 



* Lefons de Physiologie Experimentale. Paris: 1856. 



cervicnl or cervico-mnscular vein ; 17, vertebral vein ; 18, right axillary vein, cut at the 

 anterior border of the first rib ; 19. supra-sternal or internal mammary vein ; 20, left axillary 

 artery; 21, termination of the left cephalic vein; 22, left jugular; 23, right jugular; 24, 

 external maxillary or glosso-facial vein; 25, coronary vein; 26, angular vein of the eye; 27, 

 subzygomatic vein ; 28, jiosterior auricular vein ; 29. maxillo-muscular vein ; 30, internal meta- 

 carpal vein; 31, internal subcutaneous vein ; 32, radial subcutaneous vein; 33, posterior radial 

 vein; 34, basilic vein; 35, plate or cephalic vein; 36. coronary venus plexus; 37, digital vein; 

 38, internal metatarsal vein; 39, anterior root of the internal saphena vein; 40, posterior root of 

 ditto; 41, internal saphena; 42, great coronary vein; 43. small mesaraic vein; 44, different 

 branches of the threat mesaraic vein; 45, trunk of the vena porta? in its sublumbar portion, 

 lodged in the pancreas ; 46, the same in the posterior fissure of the liver — below it is seen entermg 

 the substance of the gland. M, Subscapulo-hyoideus muscle cut obliquely in the direction of the 

 trachea ; P, cervical panniculus turned down to expose the jugular furrow ; O, right auricle of the 

 heart ; a, posterior aorta : <;. section of the right lung ; F, left lobe of the liver behind the section 

 of the diaphragm; R. right kidney carried up and forward; L, oesophagus; v, bladder; s, rectum; 

 T, thoracic duct ; t'. termination of that duct in the confluent of the Jugulars. 



