20 4 



THE CIRCULATION OF THE BLOOD AND LYMPH 



are to be obtained, threads are attached to the auricle and to the apex 

 of the ventricle. The heart is suspended by fastening the cannula in a 

 holder on a stand, and the threads, after passing over pulleys to give 

 them a convenient direction, are attached to writing-levers. 



As the heart cannot now be easily kept immersed in the bath, it is 

 suspended in the air, and can be kept warm by the following simple 

 arrangement : A copper pipe about 4 inches long is slit on one side, and 

 on the opposite side is screwed or riveted to a copper rod, under which 

 is hung a spirit-lamp. The lamp is adjusted at such a point on the rod 

 that when the copper tube is placed around the heart the heat conducted 

 along the rod keeps the air around the heart at about body-temperature. 

 The perf usion liquid before it enters the heart may be heated thus : 

 A Liebig's condenser is cut through the middle, and the large end 

 closed by a paraffined cork. A glass tube is run down from the top 

 through this cork, and the aorta is attached directly to this, so that 

 the heart is very near the condenser. This tube is mostly filled up by 

 a thermometer, so that the perfusion liquid passes through it in a thin 

 stream which is easily heated by the water in the condenser, which 



contains a second ther- 

 mometer. This water is 

 kept constantly flowing 

 through the condenser 

 from a heated bath. The 

 T-piece connecting with 

 the perfusion bottles is 

 attached to the upper 

 end of the glass tube 

 to which the heart is 

 attached (Gunn and 

 Cushny) . 



15. Action of the 

 Valves of the Heart 

 (i) Study the action of 

 the valves of the ox- 



ln Y 16 ar pncial scheme, 

 as shown in Fig. 96. The 

 cavity of the heart is 

 illuminated by means of 



Fig. 9 8.-Diagram of Valves of the Heart. The 



valves are supposed to be viewed from above, the 



auricles having been partially removed. A, aorta 



with semilunar valve; B, pulmonary artery and 



valve; C, tricuspid, and D, mitral valve; E, right, 



and F, left coronary artery ; G, wall of right, and H, 



of left auricle; I, wall of right, and J, of left ventricle, a small electric lamp, the 



wires of which pass in at 



A. When the piston of the pump is pushed down, water is forced 

 through the aorta D along the tube T into the bottle, and flows back 

 again into the left auricle by the tube T'. During each stroke of the 

 pump the auriculo-ventricular valve is seen through the glass disc 

 inserted into C to close, and the semilunar valve is seen through the 

 glass in D to open. When the piston is raised, the semilunar valve is 

 seen to be closed and the auriculo-ventricular valve to be opened. 

 For comparison, a human heart with a valvular lesion might be used. 



(2) With the sheep's or dog's heart provided, perform the following 

 experiments : 



(a) Open the pericardium and notice how it is reflected around the 

 great vessels at the base of the heart. Distinguish the pulmonary 

 artery, the aorta, the superior and inferior venaj cavse, and the pul- 

 monary veins. The trachea and portions of the lungs may also be 

 attached. If so, remove them carefully without injuring the heart. 



