Chap, xvi.] THE ABDOMINAL PARIETES. 263 



posture. This cliange of surface is of importance 

 in gastrostomy, since the subjects for that operation 

 are usually much emaciated, and the incision has to be 

 made close below the costal line. 



The position of the linea alba above the umbilicus 

 is indicated by a slight median groove, but no such 

 indication exists below the navel. The linea semi- 

 lunaris may be represented by a slightly curved line 

 drawn from about the tip of the ninth costal car- 

 tilage to the pubic spine. In the adult it would be 

 placed about three inches from the navel. Above 

 the umbilicus the line is indicated on the surface by 

 a shallow depression. The outline of the rectus can be 

 well seen when the muscle is in action. It presents 

 three "liiieae trans versse," one usually opposite the 

 xiphoid cartilage, one opposite the umbilicus, and a 

 third between the two. The two upper of these lines 

 are obvious on the surface in well-developed subjects. 



The site of the umbilicus varies with the obesity of 

 the individual and the laxity of the abdomen. It is 

 always below the centre of the line between the 

 xiphoid cartilage and the pubes. In the adult it is 

 some way above the centre of the body, as measured 

 from head to foot, while in the foatus at birth it is 

 below that point. It corresponds in front to the disc 

 between the third and fourth lumbar vertebrae, and 

 behind to the tip of the third lumbar spinous process. 

 It is situated about three-quarters of an inch to one 

 inch above a line drawn between the highest points of 

 the two iliac crests. 



The anterior superior spine, the pubic spine, and 

 Poupart's ligament are all conspicuous and important 

 landmarks. The pubic spine is nearly in the same hori- 

 zontal line with the upper edge of the great trochanter. 

 It is very distinct in thin subjects. In the obese it 

 is entirely lost beneath the pubic fat. In such indi- 

 viduals, however, it can be detected, when the subject is 



