550 THE BLOOD-VASCULAR SYSTEM. 



Surface Marking. In order to map out the abdominal aorta on the surface of the abdomen, 

 a line must be drawn from the middle line of the body, on a level with the distal extremity of 

 the seventh costal cartilage, downward and slightly to the left, so that it just skirts the umbilicus, 

 to a zone drawn round the body opposite the highest point of the crest of the ilium. This 

 point is generally half an inch below and to the left of the umbilicus, but as the position of this 

 structure varies with the obesity of the individual, it is not a reliable landmark as to the situation 

 of the bifurcation of the aorta. 



Surgical Anatomy. Aneurisms of the abdominal aorta near the coeliac axis communicate 

 in nearly equal proportion Avitli the anterior and posterior parts of the artery. 



When an aneurismal sac is connected with the back part of the abdominal aorta, it usually 

 produces absorption of the bodies of the vertebrae, and forms a pulsating tumor that presents 

 itself in the left hypochondriac or epigastric regions, and is accompanied by symptoms of dis- 

 turbance in the alimentary canal. Pain is invariably present, and is usually of two kinds a 

 fixed and constant pain in the back, caused by the tumor pressing on or displacing the branches 

 of the solar plexus and splanchnic nerves ; and a sharp lancinating pain, radiating along those 

 branches of the lumbar nerves which are pressed on by the tumor ; hence the pain in the loins, 

 the testes, the hypogastrium, and in the lower limb (usually of the left side). This form of 

 aneurism usually bursts into the peritoneal cavity or behind the peritoneum in the left hypo- 

 chondriac region ; or it may form a large aneurismal sac, extending down as low as Poupart's 

 ligameiit ; haemorrhage in these cases being generally very extensive, but slowly produced, and 

 not rapidly fatal. 



When an aneurismal sac is connected with the front of the aorta near the coaliac axis, it 

 forms a pulsating tumor in the left hypochondriac or epigastric regions, usually attended with 

 symptoms of disturbance of the alimentary canal, as sickness, dyspepsia, or constipation, and 

 accompanied by pain, which is constant, but nearly always fixed in the loins, epigastrium, or 

 some part of the abdomen ; the radiating pain being rare, as the lumbar nerves are seldom 

 implicated. This form of aneurism may burst into the peritoneal cavity or behind the peritoneum, 

 between the layers of the mesentery, or, more rarely, into the duodenum ; it rarely extends back- 

 ward so as to affect the spine. 



The abdominal aorta has been tied several times, and although none of the patients perma- 

 nently recovered, still, as one of them lived as long as ten days, the possibility of the re- 

 establishment of the circulation may be considered to be proved. In the lower animals this 

 artery has been often successfully tied. The vessel may be reached in several ways. In the 

 original operation, performed by Sir A. Cooper, an incision was made in the linea alba, the 

 peritoneum opened in front, the finger carried down amongst the intestines toward the spine, the 

 peritoneum again opened behind by scratching through the mesentery, and the vessel thus reached. 

 Or either of the operations described below for securing the common iliac artery may, by extend- 

 ing the dissection a sufficient distance upward, be made use of to expose the aorta. The chief 

 difficulty in the dead subject consists in isolating the artery in consequence of its great depth ; but 

 in the living subject the embarrassment resulting from the proximity of the aneurismal tumor, and 

 the great probability of disease in the vessel itself, add to the dangers and difficulties of this for- 

 midable operation so greatly that it is very doubtful whether it ought ever to be performed. 



The collateral circulation would be carried on by the anastomosis between the internal 

 mammary and the deep epigastric ; by the free communication between the superior and inferior 

 mesenteries if the ligature were placed above the latter vessel ; or by the anastomosis between 

 the inferior mesenteric and the internal pudic when (as is more common) the point of ligature is 

 below the origin of the inferior mesenteric ; and possibly by the anastomoses of the lumbar 

 arteries with the branches of the internal iliac. 



The circulation through the abdominal aorta may be commanded, in thin persons, by firm 

 pressure with the fingers. A tourniquet has been invented for this purpose which is sometimes 

 used in amputation at the hip-joint and some other operations. 



BRANCHES OF THE ABDOMINAL AORTA. 

 Phrenic. Superior Mesenteric. Ovarian in female. 



C Gastric. Suprarenal. Inferior Mesenteric. 



Cceliac Axis. < Hepatic. Renal. Lumbar. 



( Splenic. Spermatic in male. Sacra Media. 



The branches may be divided into two sets : 1. Those supplying the viscera. 

 2. Those distributed to the walls of the abdomen. 



Visceral Branches. Renal. 



( Gastric. Spermatic or Ovarian. 



Coeliac Axis. < Hepatic. 



I Srjlenic Parietal Branches. 



Superior Mesenteric. Phrenic. 



Inferior Mesenteric. Lumbar. 



Suprarenal. Sacra Media, 



