189 



\ 



FIG. 92. DIAGRAM OF THE CIRCULATION OF THE FROG 



The veins are represented in shaded lines and those entering the heart from 

 in front are shown only on one side. A, the general circulation shown from 

 below. 



B, The heart from below, showing the venus sinus cut open. 

 ao, aorta; puv, pulmonary vein; ptc, post vena cava; 



la, left auricle; pvc, pre vena cava; vs, venus sinus, 



ra, right auricle; 



