84 ELEMENTARY BIOLOGY. [CHAP. 



5. The inferior vena cava. 



Kemove the stomach and intestine, being careful 

 not to injure the liver. The above-named vein will 

 be obvious as a large vessel lying between the 

 kidneys ; follow it forwards ; it will be seen to pass 

 behind (dorsal to) the liver, to enter the sinus 

 venosus. Its factors are — 



a. The effereiit renal veins ; a series of vessels arising 

 from the ventral faces of the kidneys. 



b. The genital veins; variable in number and detailed 

 relationships, bringing in the blood from the 

 genital glands. 



c. The hepatic veins {efferent hepatic vessels) ; two or 

 more in number, seen, on turning the liver over, 

 to enter the vena cava just before it reaches the 

 heart. 



6. The veins of the superior caval system. 



Little trouble will be found in following these if 

 the ventral portion of the shoulder-girdle and its re- 

 lated pectoral muscles be carefully removed. 



a. The superior vence cavce; short vessels seen to 

 enter the sinus venosus on either side, im- 

 mediately beneath the atrium. Each is formed 

 by the union of the three following factors. 



a. The external jugular vein, running down the 

 under side of the throat and bringing back 

 blood from the superficial parts of the head. It 

 is formed by the confluence of the lingual vein 

 from the tongue, and the itiferior 7naxillary vein 

 which skirts the outer side of the lower jaw. 



