PRACTICAL EXERCISES iBi 



will escape from the left azygos vein, which must be tied. Put on 

 any additional ligatures that may be needed to render the heart 

 water-tight. Support B in the vertical position by a clamp. Fill the 

 funnel with water, and it will rise in B to the same level as in the 

 funnel. Now compress the right ventricle with the hand, and the 

 water will rise higher in B. Relax the pressure, and notice that the 

 water remains at the higher level in B, being prevented by the semi- 

 lunar valves from flowing back into the ventricle. By alternately 

 compressing the ventricle and allowing it to relax, water can be 

 pumped into B till it escapes from its upper end, and if this is so 

 curved that the water falls into the funnel, a 'circulation' which 

 imitates that of the blood can be established. Note that during the 

 pumping the sinuses of Valsalva, behind the semilunar valves at the 

 origin of the pulmonary artery, become prominent. 



(c) Take out B and tear out one of the segments of the semilunar 

 valve. Replace B, and notice that while compression of the ventricle 

 has the same effect as before, the water no longer keeps its level on 

 relaxation, but regurgitates into the ventricle. This illustrates the 

 condition known as insufficiency or incompetence of the valves. But 



The valves are supposed to 

 be viewed from above, the 

 auricles having been partially 

 removed. A, aorta with semi- 

 lunar valve ; D, position of 

 corpora Arantii ; P, pulmonary 

 artery ; B, wall of left auricle ; 

 M t mitral valve, with i and 2 , 

 its posterior and anterior seg- 

 ments; C, wall of right auricle; 

 T, tricuspid valve, with i, its 

 posterior, 2, its anterior, and 

 3, its external segment. 



FIG. 68. DIAGRAM OF VALVES OF HEART. 



if the injury is not too extensive, it is still possible, by more vigorously 

 and more rapidly compressing the heart, to pump water into the 

 funnel. This illustrates the establishment of compensation in cases of 

 valvular lesion. 



(d) Now remove both tubes. Tie the pulmonary artery. Cut 

 away the greater part of the right auricle. Pour water into the 

 auriculo-ventricular orifice, and notice that the segments of the 

 tricuspid valve are floated up so as to close the orifice. Invert the 

 heart, and the ventricle will remain full of water. Open the right 

 ventricle carefully, and study the papillary muscles, and the chordae 

 tendinese, noting that the latter are inserted into the lower surface of 

 the segments of the tricuspid valve, as well as into their free edges. 



(e) Repeat (b\ (c\ and (d) on the left side of the heart, tying tube 

 B into the aorta as far from the heart as possible, and A into the left 

 auricle. 



(f) Separate the aorta from the left ventricle, cutting wide of its 

 origin so as not to injure the semilunar valves, and tie a short wide 



