PRACTICAL EXERCISES 



\8g 



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, recommence 

 the artificial respiration. 



(h) Connect a cylinder of oxygen with a good-sized rubber catheter, 



and pass the catheter down the 

 tracheal 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 undisturbed by 

 respiratory movements. 



(') Stop the oxygen, and 

 resume the artificial respira- 

 tion. Make a small penetrat- 

 ing wound with a scalpel in 

 the left ventricle. Observe the 



FIG. 84. 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. 



course of the haemorrhage, and note especially the difference in 

 systole and diastole. 



(/) Lay the electrodes on the heart, and stimulate it with a strong 

 interrupted current. The character of the contraction soon becomes 

 profoundly altered. Shallow, irregular contractions flicker over the 



