204 ANATOMY OF THE RABBIT. 
urethra. The main vessel leaves the pelvic cavity as the 
sciatic artery (a. ischiadica), passing to the lateral side 
of the abductor caudae anterior, and reappears posteriorly, 
dividing into the internal pudendal and lateral caudal 
arteries. 
3 The inferior caval vein (v. cava inferior) is formed on the 
dorsal surface of the posterior end of the aorta by the union of the 
paired external iliac veins with the common hypogastric. From 
this position it passes to the right side of the aorta (rarely to the 
left) almost to its ventral surface, and then runs forward on the 
right side to the diaphragm. Its visceral roots or tributaries 
(radices viscerales) comprise the paired renal and spermatic 
veins, and the hepatic veins from the liver (p. 188). Its parietal 
tributaries (radices parietales) include the inferior phrenic 
veins (vv. phrenicae inferiores), which enter the inferior cava from 
either side of the diaphragm, the lumbar veins (vv. lumbales), 
a series of vessels corresponding to the lumbar arteries, and the 
paired iliolumbar vein (v. iliolumbalis). 
4. The external iliac vein (v. iliaca externa), the continuation 
of the femoral vein of the thigh, approaches the inferior cava from 
the dorsal side of the inguinal ligament. It receives the inferior 
epigastric vein from the abdominal wall and the vesical vein 
from the bladder, the latter including in the female also the veins 
of the uterus. 
5. The sympathetic trunk (truncus sympathicus). Its lum- 
bar and sacral portions, and, with due care, its caudal portions may 
be traced on either side by working between the abdominal aorta 
(or its continuation, the median sacral artery) and the body-wall. 
Except on the ventral surface of the sacrum, the ganglia of opposite 
sides lie close together. The lumbar portion of each trunk 
comprises seven ganglia with their connections. The ganglia 
lie on the lateral surfaces of the lumbar arteries near the points 
where the latter disappear dorsally in the body-wall. The rami 
communicantes may be found passing from the ganglia toward 
the spinal nerve-roots. The sacral portion comprises four ganglia 
of which the first is much larger than the others. The caudal 
portion comprises two minute ganglia and an unpaired terminal 
ganglion uniting the two trunks. 
