Dissection of Sheep^s Heart, 155 



Heart ; and the third taking a course close under the left 

 auricle in the Auriculo-ventricular sulcus, and reaching to the 

 back of the heart and the posterior interventricular groove. 



Lastly, we may note on the exterior of the ventricles 

 several white lines running across the superficial branches of 

 the vessels ; these are Nerves derived from the Cardiac plex- 

 uses*, which are themselves derived partly from the Cerebro- 

 spinal and partly from the Sympathetic systemf. 



Turning the Heart over, the transverse groove which goes 

 round the base of the Heart between the Auricles and Yentri- 

 cles, and which is interrupted only by the trunk of the Pul- 

 monary artery anteriorly, is readily traced : the vessel in close 

 relation with and posterior to the Aorta, and opening into 

 the right Auricle at its superior border, is the Vena Cava 

 Superior, which conveys to the Heart the blood which is re- 

 turned from the Head, Neck, Upper Limbs, and Thorax, and is 

 remarkable as being a vein without valves : the vessel nearly 

 in the middle line, and terminating in the right Auricle a 

 little above its inferior margin, is the Vena Cava Inferior, 

 which returns the blood from the Lower Limbs, from the 

 Viscera, Pelvis, and Abdomen : that vessel which passes down 

 to the side of the left Auricle immediately behind the Appendix, 

 and continues its course along the back of the left Auricle and 

 Auriculo-ventricular groove to reach the lower and back part 

 of the right Auricle, on the left of the Orifice of the inferior 

 cava, close to the interauricular septum, and below and behind 

 the fossa ovalis (like the left superior cava in the lower 

 Mammalia and in Birds), is the large Left Azygos Veinp, it 



* The deep Cardiac plexus is situated inferior! y to the Trachea at its hifurca- 

 tion ; close to the point of division of the pulmonary artery, and above the 

 arch of the Aorta. The superficial Cardiac Flexus lies within the arch of the 

 Aorta and beneath the right Pulmonary artery. 



t In order to expose these more clearly, let the heart be placed in a Nitric acid 

 and spirit bath, consisting of 6| drs. of acid to one quart of spirit, for three 

 or four days. C. Robertton. 



1 J. Marshall. 



