The Frog — An Amphibious Vertebrate Animal 431 



from the base of the ventricle. A thin-walled, triangular sinus venosus, 

 located on the dorsal side of the heart, is connected with the right auricle. 

 In the adult frog the blood is pumped from the ventricle into the truncus 

 arteriosus which has branches as shown in the diagram of the arterial 

 system on page 432. Study this diagram, noting the relationships of the 

 various parts of the arterial system. 



Linqual 



■ ■ Mandibular 

 /■■ ^ 



^ Internal jagalar 



Brachial. 



Sinus 



venosus 



External jugular 



. Subscapular 



Innominate 



Cardiac- 



Hepatic 



Cutaneous — 



Posterior 

 vena cava. 



■ '' / vtA-'f V' ^^ 



-: ' y l.-v\V<S*'. . ;.<?•>.- V 



Free aval 



Spermatic. 



Dorso. lumbar. 



Renal 



^^\ Hepatic 



'> nnrf/!l 



[Gasfric 



'.Splenic 



\\ \\ !^_ / Mesenteric 



Abdominal — 

 Renal portal. 

 Vesical 



External iliac.— ^ 



Femoral 



Fig. 215. — Venous system of the bullfrog (ventral view). (Drawn by Ruth M. 

 Sanders, from Potter: Textbook of Zoology, The C. V. Mosby Co.) 



After passing from the arteries into thin-walled capillaries, the blood 

 is returned from the various tissues and organs of the body by a system of 

 veins (Fig. 215). The right and left pulmonary veins return the oxy- 

 genated (aerated) blood from the right and left lungs to the left auricle. 

 The blood from all other parts of the body is returned to the sinus veno- 

 sus through three large veins known as (1) the posterior vena cava (post- 



