DISSECTION OF THE THORAX 423 



mentum arteriosum. The arcus aortae should now be drawn 

 aside and the trachea and Nn. cardiac! exposed. Find the fol- 

 lowing nerves, which help to form the deep cardiac plexus : 



(a) From the sympathetic system: 



(aa) Middle cardiac nerve (N. cardiacus medius). 



(ab) Inferior cardiac nerve (N. cardiacus inferior). 



(b) From the N. vagus: 



(ba) Superior cardiac rami (0. T. cervical cardiac branches of 



pneumogastric). 



Is an isolated " N. depressor" present ? 



(bb) Inferior cardiac rami from the N. recurrens (rami cardiaci 



inferior es nervi recurrentis) (0. T. cardiac branches of re- 

 current laryngeal). 



Notice the subdivision of the plexus cardiacus into a right 

 and a left portion. 



How is the plexus cardiacus related to the anterior and poste- 

 rior coronary plexuses ? 



Removal of Heart. 



Divide the A. pulmonalis and the Vv. pulmonales and remove 

 the heart from the body. Continue the incision in the anterior 

 wall of the left ventricle through the ascending aorta, but make 

 sure that it passes between two of the semilunar valves. 



Valves of Aorta. 



The semilunar valves of the aorta (valvulae semilunar es 

 aortae) are now to be studied. 



(a) Posterior semilunar valve (valvula semilunaris posterior). 



(b) Right semilunar valve (valvula semilunaris dextra). 



(c) Left semilunar valve (valvula semilunaris sinistra). 



Examine the nodules (noduli valvularum semilunarium 

 [Arantii]) (0. T. corpora Arantii) and " sails" or " lunulae" 

 (lunulae valvularum semilunarium) of the valves. Examine the 

 sinus aortae [Valsalvae] from the inside and note exact origin, 

 on the inside, of the Aa. coronaria. 



Myocardium. 



Its relations to the epicardium and endocardium should be 

 reviewed. The student should study a sheep's heart or a calf's 

 heart that has been macerated in fifty per cent. HC1 or in equal 

 parts of glycerin, alcohol, and nitric acid. Or a sheep's heart 

 filled with a paste of flour and water may be boiled for fifteen 



