THE ABDOMINAL WALL 199 



parts mentioned can be felt if careful pressure is made. 

 After they have been identified the dissector should endeavour 

 to determine the position of the subcutaneous inguinal ring 

 (O.T. external abdominal). In the male it is easily defined. 

 Immediately lateral to the pubic tubercle the spermatic cord 

 can be felt as it passes over the medial end of the inguinal 

 ligament on its way to the scrotum. Take the spermatic 

 cord as a guide, push the loose skin of the scrotum upwards 

 along it before the finger, and the tip of the finger will enter 

 the ring, and will be able to distinguish its sharp lower 

 and upper margins. The most important constituent of 

 the spermatic cord is the ductus deferens. If the cord is 

 rolled between the index finger and the thumb, the duct can 

 be easily distinguished, at the back of the cord, by the hard 

 whipcord-like feel that it produces. 



The subcutaneous inguinal ring of the female is not easily 

 defined, because it is small, and the round ligament of the 

 uterus, which passes through it, is not readily felt in the fat of 

 the pubic region. 



After the inguinal region has been examined, carry the 

 index finger backwards, from the anterior superior spine of the 

 ilium, along the iliac crest The crest is easily felt ; indeed, 

 in most cases it is visible for a distance of about 65 mm. (two 

 and a half inches). At the point where it disappears from 

 view a prominent tubercle is developed on its external lip. 

 It is there, at the highest point of the iliac crest which can be 

 seen from the front, that the lateral outline of the trunk joins 

 the ilium. As will be seen later, use is made of this fact in 

 subdividing the abdominal cavity into regions. 



In females who have borne children the skin over the 

 lower part of the abdomen is wrinkled and scarred. 



Parts to be dissected. During the dissection of the 

 abdominal wall the following parts will be displayed : 



1. Superficial fascia. 



2. Cutaneous vessels and nerves. 



3. The external oblique muscle of the abdomen. 



4. The internal oblique muscle of the abdomen. 



5. The anterior branches of the lower six thoracic nerves and accompany- 



ing vessels ; the ilio-inguinal and ilio-hypogastric nerves. 



6. The transversus abdominis muscle. 



7. The rectus and pyramidalis muscles and the sheath of the rectus. 



8. The transversalis fascia. 



9. The inferior epigastric and deep circumflex iliac arteries. 

 10. The superior epigastric and musculo-phrenic arteries. 



1113 & 



