MOVEMENTS OF THE HEART. 211 



destroy only the brain and then curarise the frog. After 

 dividing the pericardium and exposing the heart, observe 



(a.) That the two auricles contract synchronously and 

 force their blood into the ventricle, which from being pale 

 and flaccid becomes red, turgid, and distended with blood. 



(b.) That immediately the ventricle suddenly contracts, 

 and forces the blood into the bulbus aortas, at the same time 

 becoming pale, while its apex is tilted forwards and upwards. 

 As the auricles continue to fill during the systole of the 

 ventricle, on superficial observation it might seem as if 

 the blood were driven to and fro between the auricles and 

 ventricle, but careful observation will soon satisfy one that 

 this is not the case. Observe very carefully how the position 

 of the auriculo- ventricular groove varies during the several 

 phases of cardiac activity. 



(c.) The slight contraction of the bulbus aortre immedi- 

 ately following the ventricular systole. 



(d.} The diastolic phase or pause when the whole heart is 

 at rest before the auricles begin to contract. 



(e.) Ligature the frsenum and divide it, tilt up the ven- 

 tricle by the ligature attached to the frsenum, and observe 

 the sinus venosus. The peristaltic wave, or wave of con- 

 traction, begins at the upper end of the vena cava inferior 

 and sinus venosus; it extends to the auricles, which contract, 

 then follows the ventricular systole and that of the bulbus 

 aortse, and finally, the pause, when the whole sequence of 

 events begins again with the systole of the sinus. 



(/) Before the ventricular systole is complete the sinus 

 is full, while the auricles are filling. 



