APPENDIX. 213 



is done, you will notice that inside the pericardium the pulmonary 

 artery lies on the ventral side of the aorta. 



9. Note the general form of the heart that of a cone with its apex 

 turned towards the diaphragm. Very carefully dissect out the entry 

 of the pulmonary veins into the heart. It will probably seem as if 

 the right pulmonary veins and the inferior cava opened into the same 

 portion of the organ, but it will be found subsequently (13. a.) that such 

 is not really the case. Note on the exterior of the organ the follow- 

 ing points: 



a. Its upper flabby auricular portion into which the veins open, 

 and its denser lower ventricular part. 



b. Running around the top of the ventricles is a band of fat, an 

 offshoot of which runs obliquely down the front of the heart, passing 

 to the right of its apex, and indicating externally the position of the 

 internal partition or septum which separates the right ventricle, 

 which does not reach the apex of the heart, from the left, which 

 does. 



c. Note the fleshy " auricular appendages" one (left) appearing 

 below the pulmonary artery; the other (right), between the aorta and 

 superior cava. 



10. Dissect away very carefully the collection of fat around the 

 origins of the great arterial trunks and that around the base of the 

 ventricles. In the fat will be found 



a. A coronary artery arising from the aorta close to the heart, 

 opposite the right border of the pulmonary artery; it gives off a 

 branch which runs in the groove between right auricle and ventricle, 

 and then runs down the dorsal side of the heart on the ventricles. 



b. The other coronary artery, considerably larger, arises from the 

 aorta dorsal to the pulmonary artery; its main branch runs along 

 the ventral edge of the ventricular septum. 



c. The coronary wins and sinus: small coronary veins will be 

 seen accompanying the arteries; for the coronary sinus see 11. c. 



11. Open the right ventricle by passing the blade of a scalpel 

 through the heart about an inch from the upper border of the ventri- 

 cle, and on the right of the band of fat marking externally the limits 

 of the ventricles, and noted above (9. &.). and then cut down towards 

 the apex, keeping on the right of this line; cut off the pulmonary 

 artery about an inch above Its origin from the lieart, and open the 

 right auricle by cutting a bit cut of its wall, to the left of the 

 entrances of the venaa cavse. On raising up by its point the wedge- 

 shaped flap cut ^rom the wall of the ventricle, the cavity of the latter 

 will be exposed. 



a. Pass the handle of a sca\pei from the ventricle into the auricle; 



