chap, xvii.] THE ABDOMINAL VESSELS. 333 



instances where it has been distended with faeces, such 

 a pain has been complained of. The pain is conveyed 

 along the obturator nerve, which lies beneath the 

 sigmoid flexure, and could be readily pressed upon by 

 that gut when diseased. 



The blood-vessels of the abdomen. Some 

 of the visceral branches of the abdominal aorta are of 

 large size, and would bleed very copiously if wounded. 

 Thus, the cceliac axis, and the superior mesenteric 

 artery, are as large as the common carotid ; the splenic, 

 hepatic, and renal vessels are about the size of the 

 brachial ; while the largest part of the inferior mesen- 

 teric trunk has dimensions equal to those of the ulnar 

 artery. Aneurisms of the aorta are especially apt to 

 occur at the cceliac axis, that being a point where a 

 number of large branches are abruptly given off, and 

 where the course of the circulation undergoes in con- 

 sequence a sudden deviation. 



When it is remembered that the lumbar glands 

 lie about the vena cava and iliac veins, it will be 

 understood that great enlargement of those bodies 

 may cause oedema from pressure. 



A number of minute but most important anasto- 

 moses exist between some of the visceral branches 

 of the abdominal aorta, and certain of the vessels 

 supplied to the abdominal parietes. These anasto- 

 moses are situated behind the peritoneum, and 

 mostly concern such viscera as have a fair surface 

 uncovered by that membrane. The visceral branches 

 that join the anastomoses are derived from the hepatic, 

 renal, and suprarenal arteries, and from the vessels 

 supplying the lower part of the duodenum, the pan- 

 creas, the caecum, and the ascending and descending 

 segments of the colon. The parietal vessels joining 

 with the above are derived from the phrenic, lumbar, 

 ilio-lumbar, lower intercostal, epigastric, and circum- 

 flex iliac trunks. In a case detailed by Professor 



