194 Anatomy of the Rabbit. 



colon (anastomosing with the middle colic), and the superior 

 haemorrhoidal artery (a. haemorrhoidalis superior) to the 

 posterior portion of the colon and the rectum. 



9. The superior mesenteric vein (v. mesenterica superior), 

 the chief tributary of the portal, collects the blood distributed by 

 the superior mesenteric artery, its tributaries being similar in 

 arrangement to the branches of the artery. The inferior mesen- 

 teric vein (v. mesenterica inferior) collects blood, from the de- 

 scending colon and. rectum ; it may be traced forward in the descend- 

 ing mesocolon. 



10. Sympathetic plexuses. In the descending mesocolon will be 

 found, the inferior mesenteric ganglion (g. mesentericum in- 

 ferius), a narrow curved body situated in front of the inferior 

 mesenteric artery- Surrounding the abdominal aorta and. appear- 

 ing in the mesocolon is the abdominal aortic plexus (plexus 

 aorticus abdominalis). It is connected anteriorly with the coeliac 

 and. superior mesenteric plexuses (p. 183) accompanying the corres- 

 ponding vessels, and. with the renal plexuses accompanying the 

 renal vessels to the kidneys; posteriorly with the inferior mesen- 

 teric and. spermatic plexuses about the inferior mesenteric 

 and. internal spermatic arteries, and with the hypogastric plexus 

 about the pelvic vessels. 



11. By dividing the rectum close in front of the pelvis, and 

 severing the peritoneal attachments, the intestines may be separ- 

 ated, and laid out in. an extended condition. The relations to one 

 another of the ileum, caecum, and colon, are studied to much better 

 advantage than in the natural position. 



VI. THE URINOGENITAL SYSTEM. 



(For the general relations of the urinogenital organs, see p. 92). 



A. The Urinary Organs. 



The central organs of excretion, the kidneys (renes), occupy an 

 anterior position on the dorsal wall of the abdomen. The right 

 kidney is placed, a little farther forward, than the left, and is largely 

 covered, by the right posterior lobule of the liver. In addition to a 

 fibrous coat immediately surrounding the kidney substance, each 

 organ is imbedded in a mass of fatty material, the adipose capsule 



