132 PRACTICAL PHYSIOLOGY 



A tracheal cammla is placed in the trachea and connected with 

 the artificial respiration apparatus. The sternum is divided in the 

 mid-line, and the thorax opened, so as to expose the heart. The 

 pericardium is slit open. Observe the systole and diastole of the 



FIG. 131. Simple model to show the effect of gravity on the circulation. 



auricular appendices arid ventricles. Ligatures are now passed under 

 the superior and inferior venae cavae and tightened. The heart 

 quickly empties. On loosening the ligatures observe the immediate 

 filling of the right heart. A ligature is next passed under the aorta 

 and tightened. Observe the engorgement, firstly, of the left, and then 

 the right heart. On loosening the ligature note the effect. A ligature 

 is next passed under the pulmonary artery and tightened. The right 

 heart becomes engorged while the left empties. On loosening the 

 ligature note the result The heart is now excised, the right ventricle 

 quickly opened. The papillary muscles may be observed contracting 

 synchronously with the ventricular wall. 



FIG. 132. Schema to show the flow in rigid and elastic tubes. (Marey.) 



The Flow in Rigid and Elastic Tubes. Arrange an experiment as 

 shown in figure 132. The two tubes are 1 metre long and of the same 

 bore, but one is a rigid tube and the other elastic. A toy-rubber balloon 



