48 THE NECTURUS 



Renal and Gonad Arteries 



The kidneys and gonads are supplied by numerous short 

 branches from the aorta at their level. These arteries are 

 numerous, short and direct. 



Caudal Artery 



Below the anus, the aorta becomes the caudal artery. It 

 is seen by cutting through on the mid-ventral line at the 

 time when the girdle is cut through to expose the iliac. 

 The caudal extends in the hasmal arches posteriorly along 

 the vertebrae, giving off branches to the anal gland and 

 the caudal muscles. 



HEART 



After the other organs have been studied, the heart may 

 be removed to complete the work on circulation. While the 

 heart is in position, study it from the ventral side. Ex- 

 amine the pericardial cavity, sinus venosus, septum 

 transversum, truncus arteriosus with its two parts, the 

 conus and bulbus, the Cuvierian duct, atria and ventricles. 



Drawing 17. Make a drawing of the heart in position to show 

 these structures. 



Remove the heart from the pericardium with plenty of the 

 body wall. First note the thin sinus venosus emptying 

 into the right atrium. 



Sinus Venosus 



The sinus receives blood from the large hepatic sinuses, 

 the posterior cardinals, and anterior cardinals. The open- 

 ing into the right atrium is large and oval in shape. 



Pulmonary 



The pulmonary veins join at the posterior side of the 

 heart and enter the left atrium by a small aperture. It is 



