PRACTICAL EXERCISES 191 



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

 funnel. Now compress the right ventricle with the frand, 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 

 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 

 tendineae, 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. 



(/) 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 

 tube into its distal end. Fill the tube with water, and notice that 

 the valves support it. Cut open the aorta just between two adjacent 

 segments of the valve, and notice the pockets behind the segments, 

 and how they are related to each other, and connected to the wall of 

 the vessel. 



15. Sounds of the Heart. (a) In a fellow-student notice the 

 position of the cardiac impulse, the chest being well exposed. Use 

 both a binaural and a single-tube stethoscope. Place the chest-piece 

 of the stethoscope over the impulse, and make out. the two sounds 

 and the pause, (b) With the hand over the radial or brachial artery, 

 try to determine whether the beat of the pulse is felt in the period 

 of the sounds or of the pause, (c) Listen with the stethoscope over 

 the junction of the second right costal cartilage with the sternum, 

 and compare the relative intensity of the two sounds as heard here 

 with their relative intensity as heard over the cardiac impulse. 



1 6. Cardiogram. Smoke a drum, and arrange a recording tam- 

 bour and a time-marker beating half or quarter seconds to write 

 on it (Fig. 76, p. 179). Apply the button of a cardiograph (Fig. 22, 

 p. 82) over your own cardiac impulse, and fasten it round the body 

 by the bands attached to the instrument. Connect the cardiograph 

 by an indiarubber tube with a recording tambour (Fig. 86) . Set the 

 drum off at a fast speed, take a tracing, and varnish it. Compare 

 with Fig. 23 (p. 83), and if the tracing is sufficiently typical, as is 



