HEART OF THE MAMMAL 1 



1. Examine a Pig's heart and note that it is conical in form, with a 

 broad base and a narrow apex. Place it with the apex pointing toward you 

 and note the following external features : (a) the left ventricle, with 

 very thick, muscular walls, continuing to the tip of the apex; (b) the 

 right ventricle, with thinner walls, lying beside the left ventricle except 

 near the tip, which is entirely formed by the left ventricle ; (c) the left 

 auricle ; and (d) the right auricle, both lying anterior to the ventricles. 

 Both of the auricles are smaller and have much thinner walls than the 

 ventricles, and each is provided with (e) an ear-like flap of tissue (auricu- 

 lar appendage). 



2. Explore the cavity 2 of the left auricle, noting (a) the openings of the 

 pulmonary veins, and (6) the opening into the left ventricle. 



3. Explore the cavity of the left ventricle, noting : (a) the very heavy, 

 muscular walls ; (b) the mitral valve, guarding the opening from the 

 auricle, the edges of which are attached to (c) elevations (papillary 

 muscles) of the muscular walls of the ventricle by a number of (d) fine 

 tendinous cords (chordae tendineae). Feel with your finger and find 

 (e) the opening into the aorta. Study the aorta, noting (/) its heavy, 

 elastic walls; (g) the semilunar valves; and (h) the opening of the 

 coronary artery just beyond the valves. 



4. Explore the cavity of the right auricle, noting (a) the large openings 

 from the venae cavae ; (b) the small opening of the coronary vein just 

 posterior to the former ; and (c) the opening into the right ventricle. 



5. Explore the cavity of the right ventricle, noting (a) the thinness of 

 the walls as compared with the left ventricle ; (b) the tricuspid valve 

 which shows the same structure as the mitral valve. Find the opening into 

 (c) the pulmonary artery, which contains (d) semilunar valves, the 

 same as in the aorta. 



6. Make a drawing of the heart from the left side, showing as many as 

 possible of the observed structures. 



» B. pp. 193-194. 



2 The various chambers of the heart should be opened by making a longitudinal 

 incision through the walls. 



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