DISSECTION OF THE l><><; 



41 



Thus constituted, the portal vein makes directly for the porta of the liver, 

 and has been previously seen in relation t<> the hepatic artery and the bile 

 duct. ( Jlose to the porta it is joined by I li<- gasl i<» duodenal rein, and generally 

 also by a fair sized vessel from the pancreas. 



Within the liver the portal vein comports itself after the manner of an 

 artery ; thai is to say. it repeatedly divides and finally ends in capillary spaces, 



Or sinusoids, between tile microscopic eells of the liver. 



Dissection. Strip the mediastinal pleura from the surface of the pericardium 

 and expose the phrenic nerves. At the same time the fat tying in the 



precardial mediastinum should be removed, in order t hat. t lie entire length 



r v. gastro-dnodenalis 



v. pancreatico-duodenalis 



_r. gaslro-epiploica 

 dexlra 



\ v. mesenteric*! cranialis 



v. mesenterial caudal is 

 v. licnalis 

 r. gaslro-epiploica sinistra 



Fig. 14. — Portal vein : semi-diagrammatic. 



of the phrenic nerves may be demonstrated. If the subject be a young 

 one, the thymus should be found in this position. Other structures to be 

 sought are the pericardiaco-phrenic, thymic, and mediastinal branches of 

 the internal mammary artery. 



A. mammakia INTERNA. — The greater part of the internal mammary artery 

 has already been examined. Its origin, the first part of its course, and some 

 of its earlier branches remain for consideration. The internal mammary is a 

 branch of the subclavian artery and arises at the first rib. From this point 

 it runs obliquely in a caudal and ventral direction in the precardial mediastinum, 

 and thus reaches the sternum, where its relationship to the transverse thoracic 

 muscle begins. The collateral branches now to be dissected are as follows : 



(1) The pericardiaco-phrenic artery (a. pericardiaco-phrcnica) is often very 



