THE THORAX 1051 



to the left nerve, and forms the right posterior pulmonary plexus, from which 

 it emerges as two cords, and these, as on the left side, descend to the oeso- 

 phagus. 



The lungs having been replaced in position, the root of each is now to be 

 fully dissected, the bronchus, pulmonary artery, and pulmonary veins being 

 clearly separated from each other all round the root. In performing this 

 dissection the anterior and posterior pulmonary plexuses of nerves, already 

 referred to, are to be studied, and the bronchial lymphatic glands are to be 

 displayed. These glands are usually quite black, this being due to the 

 deposit of carbonaceous matter in them. The general relations of each root, 

 and the special relations of the chief constituents, are to be thoroughly 

 mastered. 



The right and left pulmonary arteries should now be examined from their 

 origin from the main trunk to the root of each lung, and their relations are 

 to be noted, as well as the ligamentum ductus arteriosi in connection with 

 the root of the left pulmonary artery. The pulmonary veins on each side 

 are also to be followed from the root of the lung to the back part of the left 

 auricle of the heart. In the dissection of the roots of the lungs the bronchial 

 arteries, one right and two left, and the bronchial veins are to be kept in 

 view. 



Exterior of the Heart. — The dissection of the heart is now to be proceeded 

 with. Its external form is to be carefully examined ; the directions of the 

 base, apex, and borders are to be observed ; and the grooves by which it is 

 divided into auricular and ventricular portions, and these, in turn, into right 

 and left auricles, and right and left ventricles, are to be noted. The apex 

 will be seen to be formed entirely by the left ventricle. 



The right and left coronary arteries are to be fully dissected, and their 

 origins from the root of the ascending aorta clearly shown, the trunk of the 

 pulmonary artery being displaced as may be required. The right coronary 

 artery is to be followed along the front and back of the right auriculo-ven- 

 tricular groove, and its marginal branch is to be shown passing along the 

 margo acutus. On the back of the heart the main vessel will be found to 

 divide into two terminal branches, transverse and descending. The trans- 

 verse branch is to be followed into the back part of the left auriculo-ven- 

 tricular groove, where it anastomoses \vith the transverse branch of the left 

 coronary artery ; and the descending branch is to be followed along the 

 inferior interventricular groove as far as the region of the apex, where it 

 anastomoses with the descending branch of the left coronary artery. 



The left coronary artery is to be shown dividing very early into a trans- 

 verse and descending branch on the left side of the root of the pulmonary 

 artery. The transverse branch is to be followed round the left auriculo- 

 ventricular groove, and its marginal branch is to be shown parsing along 

 the margo obtusus vel rotundus. The descending branch is to be followed 

 along the antero-supericH" interventricular groove as far as the region of the 

 apex. 



In dissecting the coronary arteries the right and left coronary plexuses 

 of nerves are to be kept in view, and the various cardiac veins are to be at 

 the same time displayed. 



In the back part of the left auriculo-ventricular groove the coronary sinus, 

 about I inch leng, will be found, and its dUated condition is to be noted. 

 The great cardiac or coronary vein (anterior interventricular vein) will be 

 found in the antero-superior interventricular groove, along with the de- 

 scending branch of the left coronary artery. On entering the front part of 

 the left auriculo-ventricular groove (where it is now strictly the great cardiac 

 or coronary vein), it should be followed, in company with the transverse 

 branch of the left coronary artery, to the back part of the groove, where it 

 will be found to become continuous with the coronary sinus. The middle 

 cardiac vein (posterior interventricular vein) \\'ill be met \\-ith in the inferior 

 interventricular groove, where it accompanies the descending branch of the 

 right coronary artery, and it should be shown to join the right extremity of 

 the coronary sinus. The right or small cardiac or coronary vein will be 



