204 



THE CIRCULATION OF THE BLOOD AND LYMPH 



and filling of the heart. Repeat the observation with head up and 



feet down. 



(e) Compress the aorta with the fingers, and observe the effect on 



the degice of dilatation of the various cavities of the heart. Repeat 



the experiment with the inferior vena cava, and compare the results. 



(/) Smoke a drum. Insert the 

 hooks of the myocardiograph (Fig. 95) 

 into the ventricle, taking care not 

 to penetrate deeply into the -wall. 

 Arrange the lever to write on the 

 drum. While a tracing is being 

 taken stimulate the peripheral end of 

 the vagus. Unhook the cardiograph. 

 (g) Stop the artificial respiration, 

 and observe the changes which take 

 place in the auricles and ventricles, 

 comparing particularly the right side 

 of the heart with the left. Before 

 the heart has stopped beating, re- 

 commence the artificial respiration. 



(h) Connect a cylinder of oxygen 

 with a good-sized rubber catheter, 



'C 



Fig. 96. Arrangement to illustrate Action of Cardiac Valves in the Heart of an Ox 

 (Gad). C, glass window in left auricle; D, window in aorta; E, tube inserted 

 through apex of heart into left ventricle and connected with pump P; A, side 

 tube on E, through which wires are connected with a'tiny incandescent lamp in 

 the ventricle; W, water in bottle B; T, T', tubes. 



and pass the catheter down the trachea! cannula or through a separate 

 opening in the trachea. Allow a small stream of oxygen to flow into 

 the lungs. Artificial respiration is now unnecessary. The lungs 

 remain at rest, yet the blood is sufficiently oxygenated, and the heart 

 goes on beating. The myocardiographic tracing thus goes on undis- 

 turbed by respiratory movements. 



(i) Stop the oxygen, and resume the artificial respiration. Make a 



