214 TEE HUMAN BODY. 



and also from the ventricle into the pulmonary artery, and make out 

 thoroughly the relations of these openings. 



b. Slit open the auricular appendage; note the fleshy projections 

 (column carnece) on its walls, and the smoothness of the rest of the 

 interior of the auricle. Observe the apertures of the vena cavce, 

 and note that the pulmonary veins do not open into this auricle. 



c. Behind or below the entrance of the inferior cava, note the 

 entrance of the coronary sinus; pass a probe through the aperture 

 along the sinus and slit it open; notice the muscular layer covering 

 it in. 



12. Raise up by its apex the flap cut out of the ventricular wall, 

 and if necessary prolong the cuts more towards the base of the ven- 

 tricle until the divisions of the tricuspid valve come into view. 



a. Note the columnae carneaB on the wall of the ventricle, and the 

 muscular cord (not found in the human heart) stretching across its 

 cavity. Also the prolongation of the ventricular cavity towards the 

 aperture of the pulmonary artery. 



b. Cut away the right auricle, and examine carefully the tricuspid 

 valve, composed of three membranous flexible flaps, thinning away 

 towards their free edges; proceeding from near these edges are strong 

 tendinous cords (chordae tendincce), which are attached at their other ends 

 to muscular elevations (papillary muscles) of the wall of the ventricle. 



c. Slit up the right ventricle until the origin of tlie pulmonary 

 artery comes into view. Looking carefully for the flaps of the semi- 

 lunar valves, prolong your cut between two of them so as to open the 

 bit of pulmonary artery still attached to the heart. Spread out the 

 artery and examine the valves. 



d. Each flap makes, with the wall of the artery, a pouch, opposite 

 which the arterial wall is slightly dilated. The free edge of the 

 valve is tmued from the heart, and has in its middle a little nodule 

 (corpus Arantii). 



13. Open the left ventricle in a manner similar to that employed 

 for the right. Then open the left auricle by cutting a bit out of its 

 wall above the appendage. Cut the aorta off about half an inch 

 above its origin from the heart. The aperture between left auricle 

 and left ventricle can now be examined; also the passage from the 

 ventricle into the aorta, and the entry of the pulmonary veins into 

 the auricle; and the septum between the auricles and that between 

 the ventricles. 



a. Pass the handle of a scalpel from the ventricle into the auricle; 

 another from the ventricle into the aorta; and pass also probes into 

 the points of entrance of the pulmonary veins. Observe that no other 

 veins open into this auricle- 



