ABDOMINAL WALL 377 



the two recti muscles. It is an important line to the 

 surgeon, because here the wall of the abdomen is thin and 

 devoid of blood-vessels. In this line the trocar is intro- 

 duced into the abdomen in the operation of paracentesis 

 abdominis or tapping. 



In the linear depression, rather nearer the pubes than 

 the ensiform cartilage, is the umbilicus or navel. This is a 

 depressed and puckered cicatrix, the floor of which is raised 

 in the form of a little button-like knob. It results from the 

 closure of an opening, in the abdominal wall of the foetus, 

 through which passed the constituents of the umbilical cord 

 viz. the umbilical vein, the two allantoic or umbilical 

 arteries, and the stalk of the allantois. 



In powerful, well -developed subjects the rectus muscle 

 stands out on each side of the middle line, and its lateral 

 margin gives rise to a curved line, the concavity of which is 

 directed medially. This line corresponds to the linea semi- 

 lunaris i.e. the line along which the aponeurotic tendon of 

 the internal oblique muscle splits to enclose the rectus. The 

 linea semilunaris may, on certain occasions, be selected by the 

 surgeon as the site for incisions through the abdominal wall. 



The student should now place his finger upon the upper 

 part of the symphysis pubis and carry it laterally, over the 

 pubic crest, to the pubic tubercle ; from this he should follow 

 the line of the inguinal ligament (Poupart's) to the anterior 

 superior spine of the ilium, and, having identified these parts, 

 he should next endeavour to determine the position of the 

 subcutaneous inguinal ring (O.T. external abdominal). This 

 is easily done in a male subject. Immediately lateral to the 

 tubercle of the os pubis the spermatic cord can be felt as it 

 passes over the inguinal ligament to reach the scrotum. 

 Taking this as a guide, push the loose skin of the scrotum 

 upwards before the finger. The tip of the finger enters the 

 opening, the sharp margins of which can now be felt. 



The spermatic cord, as it passes downwards into the 

 scrotum, should be taken between the finger and thumb. 

 On pressure being applied the ductus deferens can be easily 

 distinguished at the back of the cord, by the hard whipcord- 

 like feel that it conveys to the fingers. 



The crest of the ilium, as it proceeds upwards and back- 

 wards from the anterior superior spine, can be easily felt. 

 Indeed, in most cases, it is visible to the eye for a distance 



