THE CAT 223 



opening, is a slight elevation, the clitoris, which is the structural 

 homologue of the penis of the male. 



Exercise 14. Draw a semidiagrammatic view of the genital organs. 



The Vascular System {Continued) ; the Caval Veins. We shall 

 now begin to study the veins which carry venous blood directly 

 to the heart. Three groups .of these veins are present: (1) the 

 precaval vein and its branches, which bring blood from the forward 

 part of the body; (2) the postcaval vein and its branches, which 

 bring blood from the hinder part of the body ; and (3) the coronary 

 veins, which bring blood from the walls of the heart itself. 



The Postcaval System. The anterior, thoracic portion of the 

 postcaval vein will be observed later, when the organs of the 

 thoracic cavity are studied. Its abdominal portion arises in 

 the hinder part of the abdominal cavity and passes forward near 

 the median plane between the kidneys to the right lobe of the 

 liver, through which it passes. It then pierces the diaphragm and 

 enters the thoracic cavity. 



Press the liver back and observe this large vein passing through 

 the diaphragm from the liver. Press the liver forward and note 

 where the vein enters it from behind. Find the two renal veins, 

 which come to it from the kidneys. The postcaval will be seen to 

 be formed in the hinder part of the abdomen by the union of 

 two large veins, the common iliacs, which bring blood from the 

 hind legs. 



As the vein passes forward from this point it receives the follow- 

 ing veins, all of which are paired, although the members of a pair 

 do not always meet the postcaval in the same transverse plane: 

 the iliolumbar veins, which join the postcaval just in front of the 

 common iliacs, coming from the lumbar muscles; the spermatic 

 veins (in the male) or the ovarian veins (in the female), which 

 join the postcaval just behind the kidneys (the left vein often 

 going to the left renal vein instead of to the postcaval) ; the renal 

 veins, which bring blood from the kidneys; the adrenolumbar 

 veins, which meet the postcaval just in front of the renal veins, 

 bringing blood from the abdominal wall and the suprarenal bodies ; 

 the hepatic veins (variable in number), which enter the postcaval 



