ABDOMEN. 



231 



8. Extent, from external to internal abdominal ring. 



9. Location of internal ring, one-half of an inch above Poupart's ligament and 

 midway between symphysis pubis and anterior superior iliac spine. 



10. Length of canal, one and one-half inches. 



Having learned the above thoroughly, cut through the external wall and 

 expose the canal, as in figure 161. 



Coverings of the Spermatic Cord and Testicle. Pass your finger down 

 into the scrotum anterior to the cord ; cut through the skin and fascia and 

 expose the testicle and find the following coats : 



1. The skin and superficial fascia. 



2. The dartos, consisting of muscular and contractile tissue. 



3. The intercolumnar fascia, part of external oblique. 



4. The cremasteric fascia, part of the internal oblique. 



5. The infiindibuhnn, part of transversalis fascia. 



6. The tunica vaginalis, part of the peritoneum. 



You will then look upon these coats as small parts of the individual con- 

 stituents of the abdominal walls pushed ahead of the testicle in its descent. 

 The tunica vaginalis was pushed ahead, a part of the peritoneum ; the infundi- 

 bulum, a part of the transversalis fascia; the cremaster, apart of the internal 

 oblique ; the intercolumnar fascia, a part of the external oblique ; the dartos, a 

 part of the superficial fascia, slightly modified by the presence of elastic fibres 

 and muscle fibres ; the skin to form the scrotum. 



The Spermatic Cord. In front of the cord find the ilio-inguinal nerve ; be- 

 hind the cord the genital branch of the genito-crural nerve. Find the excretory 

 duct of the testicle the vas deferens ; the spermatic artery, a branch of the 

 aorta ; the spermatic veins ; a little artery the deferential in the sheath of the 

 vas deferens. These structures are all bound loosely together by connective 

 tissue. You will trace all these structures to the testicle. 



Next expose the internal oblique muscle by turning aside the external ob- 

 lique in this manner : Divide the digitations at their attachments into the eight 

 lower ribs. Turn the whole muscle forward and see the internal oblique. Its 

 fibres run upward and inward. This is also called ascending oblique. 



The Internal Oblique (Fig. 160). This muscle has attachments : (i) To 

 the outer surface of the four lower ribs ; (2) to the middle lip of the crest of the 

 ilium ; (3) to the outer one-half of Poupart's ligament ; (4) to the pubic crest 

 and ilio-pectineal line ; (5) to the linea alba. Notice, first, the arch formed by this 

 muscle and the transversalis. In figure 160 you see these muscles are attached 

 to Poupart's ligament for about the outer one-half the length of this ligament; 

 then they leave this ligament, arch over the cord, form the roof of the inguinal 

 canal, and are inserted into the pubic crest by the conjoined tendon. Trace this 

 muscle to the middle lip of the iliac crest, anterior two-thirds. 



Make an incision, parallel to the iliac crest, through this muscle, and you will 

 come down upon the neuro-vascular area of the abdominal walls. These vessels 

 and nerves are between the internal oblique and transversalis, in a small quantity 

 of fatty connective tissue, and are as follows : 



1. Deep circumflex iliac artery, from the external iliac. 



2. Ilio-hypogastric nerve, from the lumbar plexus. 



3. Ilio-inguinal nerve, from the lumbar plexus. 



4. Lower intercostal nerves, the twelfth thoracic. 



It will require care to separate these muscles. The guide is this : Keep the 

 nerves in sight and follow them. Now trace the internal oblique muscle to the 

 outer surface of the four lower ribs. Notice the direction taken by the muscular 

 fibres. See also that the fibres of this muscle are attached to the outer one-half 

 of Poupart's ligament, with the transversalis, and that both are inserted by a 



