242 



THE MESODERMAL DERIVATIVES 



cava as it enters the sinus venosus. These changes leave the ductus 

 Cuvieri connected with only the anterior or superior vena cava, which 

 may now be called the pre-caval vein. 



Posteriorly the vessel produced by fusion of the posterior cardinal 

 veins, now considered as the median cardinal vein, is enlarged as 



COMMON CARDINAL V. 

 PRE CAVAL V. 



SINUS VENOSUS 



RIGHT AURICLE 



INFERIOR VENA CAVA^ 

 (POST. VENA CAVA) 



ANTERIOR PART RIGHT 

 POST. CARD. DEGENERATES 



INTERNAL JUGULAR V. 



EXTERNAL (SUPERIOR) 

 JUGULAR V (ANT CARO.V.) 



INTERAURICULAR SEPTUM 



LEFT AURICLE 



ATRIO VENTRICULAR VALVE 

 VENTRICLE 



'^PULMONARY V. 



I DEGENERATING ENTIRE 

 LEFT POST CARD. V 



♦'KIDNEY 



SUBCARDINAL 

 (RENAL PORTAL) V, 



VITELLINE {HEPATIC PORTAL) V. 



Blood vascular system of the frog tadpole. Venous system, ventral view. 



( Continued on f(icini> pa(^e.) 



