1068 DISSECTION OF THE THOEAX. 



being cleared away from the trunks of vessels entering and emerging 

 from the heart. The arch of the aorta may now be fully studied, 

 and the cord of the ductus aiteriosus displayed passing between the 

 commencement of the left pulmonary artery and the arch of the aorta 

 (pp. 331 and 382). The students will then proceed to the dissection 

 of the heart, examining first its external form (p. 302), and afterwards 

 dissecting the right and left coronary arteries and the .coronary vein (pp. 

 338 and 482). They will then make an opening into the right auricle, 

 by means of one incision from the point of entrance of the vena cava 

 superior to near the entrance of the vena cava inferior, and another from 

 the auricular appendage to the middle of the first incision. They will remove 

 and wash out the blood from the right side of the heart, and will particularly 

 observe in the auricle the arrangement of the musculi pectinati, the annulus 

 ovalis, the Eustachian valve guarding the vena cava inferior, the orifice of the 

 coronary vein guarded by the valve of Thebesius, and the foramina Thebesii 

 (p. 308). When the examination of the right auricle has been completed, the dis- 

 sector will pass the forefinger of the left hand through the auriculo- ventricular 

 orifice, and open the right ventricle by two incisions, one along the anterior 

 border, close to the septum of the heart, prolonged upwards to the com- 

 mencement of the pulmonary artery, and the other passing from the first, 

 along the superior border of the ventricle, immediately below the auriculo- 

 veutricular sulcus, care being taken not to injure the anterior segment of 

 the tricuspid valve. The principal objects to be noted in this ventricle are 

 the tricuspid valve with the chordae tendinese and musculi papillares which 

 act upon it, the other arrangements of columnse carnese, the infundibulum, 

 and the semiluuar valves of the pulmonary artery on their cardiac aspect. 

 In exposing the latter, the incision into the ventricle should be carried into 

 the pulmonary artery between two of the segments of the valve (p. 310). 

 To examine the left side of the heart, let the inferior vena cava be dissected 

 a little out of its aperture in the diaphragm, and let it be divided, and the 

 heart thrown up\\ ards. The left auricle is then to be opened by a transverse 

 incision near its ventricular margin, and by two short incisions at right 

 angles to the first ; and after being carefully sponged out, its cavity and 

 auricular appendage, the remains of the valve of the foramen ovale, and 

 the entrance of the pulmonary veins on each side will be examined (p. 

 311). The left ventricle is to be opened by a process similar to that 

 employed for opening the right ; and after it is carefully cleaned, the 

 mitral valve and its relation to the aortic orifice, and the cardiac aspect 

 of the semilunar valves which guard the latter are to be studied (p. 312). 



4. Deep Cardiac Nerves, Bronchi, <&c. The aorta is to be divided 

 within an inch above its origin, and the first part of the vessel is to be 

 opened to examine the semilunar valves and the sinuses of Valsalva (p. 

 307). At this stage of the dissection a fuller examination may be made 

 of the cardiac neives as they enter the superficial and deep cardiac 

 plexus : the cardiac ganglion will also be found, and the coronary plexus 

 traced a short way along the coronary vessels (p. 698). The dissectors 

 may then divide the trachea an inch or two above its bifurcation, remove 

 the heart and lungs, and examine more in detail the disposition and struc- 

 ture of the bronchi (p. 888). 



5. Parts in the posterior mediastinum, <&c. Returning to the thoracic 

 cavity, the dissectors will examine the oesophagus (p. 821), the descending 

 aorta with its intercostal branches (p. 401), the main vena azygos, and its 

 left branch (p.4G9) and, lying between the vena azygos and aorta, the thoracic 



