34 Practicum V. The Left Ventricle. 



>J 1 8. With the scissors cut from the auricle through the ventricular 

 wall near the septum ; then divaricate the sides. 



a. The auriculo-ventricular orifice is surrounded by what seems at 

 first a continuous VALVE ; this, may, however, be divided somewhat arbi- 

 trarily into two parts, a SEPTAL, applied against the septum and a LAT- 

 ERAL, opposite it ; hence they are called BICUSPID or MITRAL. 



b. Note the CHORD/E TENDINE^E and COLUMNS CARNEY as in the 

 right ventricle ; PI. XIV. 



c. Remove part of the lateral wall of the ventricle and note on the 

 cut surfaces the ends of the CARDIAC VESSELvS as in PL XIV. 



19. The Aorta, Trim off the remnants of the right auricle and 

 ventricle. Slit the septal bicuspid valve for half its length, and note 

 that it covered a large orifice, the MOUTH OF THE AORTA, surrounded by 

 three SEMILUNAR VALVES. 



a. Pass a flexible probe thence out of the cut end of the aorta or its 

 branch, or make two stiff probes meet half way. 



b. Remove the lateral wall of the aorta and its branch to near the 

 level of the pulmonary valves. 



S 20. The Ductus Arteriosus. Where the aorta crosses the pulmon- 

 ary artery look for a slight depression or foramen, the aortic end of the 

 DUCTUS ARTERIOSUS, through which, in the fetus, the blood from the 

 right ventricle entered the aorta from the pulmonary artery at the point 

 so marked (obscurely) in PI. 12. Tear the two vessels apart carefully and 

 look for the remnants of the tube. If it is found pervious the instruc- 

 tor's attention should be called to it. 



21. The Aortic Arch. These resemble the semilunar valves 

 already seen in the pulmonary artery. One is ventral, the other two 

 right and left. 



a. Pass a scissors-blade between the ventral and right valves ; cut 

 the ventricular septum and divaricate the sides. 



b. The right sinus of Valsalva resembles those in the pulmonary- 

 artery. 



22. The Cardiac Arteries. The left and ventral sinuses of val- 

 salva present each a circular orifice the adit of a cardiac or coronary 

 artery. 



a. These arteries supply the substance of the heart with blood. The corresponding 

 veins were mentioned in 8. These arteries and veins are the intrinsic blood-vessels of 

 the heart. 



b. Commonly there is one arterial orifice at each sinus ; sometimes two or even three. 



c. The arteries may be traced for a short distance only in the dissected specimen. 



i? 23. If time permits make drawings of various aspects of the dis- 

 section. 



