262 Anatomy Applied to Medicine and Surgery. 



Landmarks. From a point in the middle line of 

 the body and about one inch below the bony ends of the 

 seventh ribs, draw a line to a point a little to the left of 

 the middle line, and half an inch below the level of the 

 umbilicus. The level of the umbilicus may be more or 

 less altered in cases of obesity, so that a better landmark 

 for the lower end of the vessel would be a point a little to 

 the left of the middle of the line joining the highest parts 

 of the crests of the ilia. 



The landmarks for the main branches of the aorta are 

 as follows : The coeliac axis is opposite the lower border 

 of the twelfth dorsal vertebra and is about four inches 

 from the umbilicus. The superior mes enteric arises op- 

 posite the lower part of the first lumbar vertebra, a little 

 less than four inches above the umbilicus. The renal is 

 opposite to the intervertebral substance between the first 

 and second lumbar vertebrae, and about three and a half 

 inches above the umbilicus, while the inferior mesenteric 

 is opposite the middle of the third lumbar and about one 

 inch above the umbilicus. 



Aneurism of the abdominal aorta is much less com- 

 mon than aneurism of the thoracic, since, according to 

 Crisp, only fifty-nine, out of a total of five hundred and 

 eighty-one cases of aortic aneurism, were abdominal. The 

 upper part of the abdominal aorta is more frequently in- 

 volved in this condition than the lower part, as shown by 

 Sebert, who noted that out of one hundred and three cases 

 of abdominal aneurism only three were at or near the 

 bifurcation (Pepper). Should rupture of the sac occur 

 in this variety of aneurism it may take place into the retro- 

 peritoneal tissue, or into the peritoneal cavity, or into the 

 stomach, bowels, bladder, vena cava, pleural cavity or 

 spinal canal. Among the symptoms of abdominal anuer- 

 ism, pain of a severe neuralgic character occupies a promi- 



