THE FROG-HEART 



65 



receiving the two vense cavas superiores and the vena cava inferior ; 

 above, it is continuous with, but marked off by a whitish line (the 

 sino-auricular junction) from, the auricle, which is double and receives 

 on the left side the pulmonary vein ; the two auricles open into a 



Aortic trunk. 



Left auricle. 

 Pulmonary vein. 



Sinus venosus. 



Superior (ant.) vena cava. 

 Bight auricle. 



Bulb of aorta. 

 Coronary sulcus. 



Pericardial fold with vein. 

 Vena cava inf. (post.). 



Fid. 56. HEART OP FROG PROM DORSAL ASPECT (GAUPP). ? 



single ventricle. On the front the bulbus aortse is seen leaving the 

 ventricle and dividing into two trunks, the right and left aortse, 

 each of which again soon divides into three branches. 



Notice that with each systole the venous part of the heart (sinus 

 venosus) contracts first ; its contraction is immediately, followed by 



Ext. jugular vein. 



Superior (ant.) vena cava. 



Bight pulmonary vein. 

 Sinus venosus. 



Innominate vein. 



Subclavian vein. 

 Bight auricle. 

 Bulb of aorta. 

 Coronary sulcus. 



Pericardial fold with vein. 



Ventricle apex. 

 FIG. 57. HEART OP FROG, SEEN PROM THE BIGHT SIDE (GAUPP). 5. 



that of the auricles, which contract together, and this by that 

 of the ventricle. In a frog the spinal cord of which has been 

 destroyed, there is usually little or no blood passing through the 

 heart. But if blood is being pumped through, notice the sudden 

 distension (diastole) of each cavity which immediately succeeds 

 its contraction (systole). If the finger be very lightly placed on the 

 ventricle the hardening which accompanies systole may be felt. 



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