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PEACTICAL PHYSIOLOGY 



ligature note the result. If the origin of the pulmonary artery and 

 aorta be forcibly compressed between thumb and finger, the second 

 sound of the heart disappears. If the index finger be placed behind 

 the aorta and pulmonary artery, and the thumb at the level of the 

 auriculo-ventricular groove, and the heart be thus forcibly compressed, 

 the filling of the heart will be prevented. The first sound continues 

 to be heard feebly, while the second sound ceases. 



The heart is now excised, the right ventricle quickly opened. The 

 papillary muscles may be observed contracting synchronously with the 

 ventricular wall. The first sound may be heard in the excised heart. 



FIG. 99. 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 99. The two tubes are 1 metre long and of the same 

 bore, but one is a rigid tube and the other elastic. The small outflow 

 orifices are made as nearly as possible of the same size. Rhythmically 

 open and shut the compressor. The flow from the rigid tube is inter- 

 mittent, while from the elastic tube it is continuous. The latter 

 delivers more fluid in one minute than the former. Change the 

 outflow orifices to eliminate this source of error and repeat the 

 experiment. Feel the pulse in the elastic tube. Observe that the 

 outflow from it becomes intermittent when the outflow orifice is 

 enlarged. The increased and continuous flow from the elastic tube is 

 due to the potential energy stored up in the stretched wall of the tube, 

 which maintains the flow during diastole. 



The Artificial Schema. The two ends of a Higginson syringe B are 

 connected with a long rubber tube. The middle of the tube divides 

 into two channels; (1) a glass tube filled with shot representing the 



