204 



THE FROG— THE PLATANA 



2. Note the inferior vena cava (postcaval vein) receiving the renal veins 

 from the kidneys and the hepatic veins from the liver, and opening into the 

 sinus venosus. 



Precaval vein 



Ventricle, 

 Sinus venosus 



— Liver 



-Hepatic portal- 

 Abdominal 

 -Abdominal 



Ventricle, 

 Sinus venosu$ 

 Livet, 



Precaval vein 



A B 



Fig. 70. — A. Venous System (posterior part) of Rana; and B. of Xenopus, from the ventral 

 aspect. The ventricle of the heart is tilted forwards to show the sinus venosus. The veins 

 of the legs, being on the dorsal side, are shown in broken lines, 



3. In order to make out the femoral and sciatic veins, turn the Frog over so 

 as to have the dorsal surface uppermost. Carefully separate the rectus anticus 

 femoris muscle from the vastus externus muscle so as to expose the femoral 

 vein ; it lies between the vastus internus and the vastus externus, where it may 

 be traced back a short distance, then gradually towards the inside of the thigh, 

 under the vastus externus and biceps muscles. It follows the course of the 

 biceps muscle, passing on to the ventral surface of the leg at the knee, just 

 where the gastrocnemius muscle meets the semimembranosus. 



Note the ramus communicans iliacus, a small vein on the anterior dorsal 

 surface of the thigh just at the origin of the vastus externus muscle. It is a 

 vessel communicating between the femoral and the sciatic veins. 



Carefully separate the biceps muscle from the semimembranosus so as to 

 expose the sciatic nerve. It divides into two branches at the anterior end of 

 the biceps. The main branch, next the biceps muscle, divides just above the 

 knee into the tibial and peroneal nerves supplying the leg and the foot respec- 

 tively ; the other branch passes under the semimembranosus, and, as it supplies 

 that muscle, it may be named the semimembranosus nerve. Following the 



