THE ABDOMINAL WALL 



213 



must be preserved. Close to the iliac crest the lateral branches 

 of the ilio-hypogastric and last thoracic nerves emerge from the 

 midst of its fleshy fibres, whilst anteriorly it is pierced by the 

 anterior branch of the ilio-hypogastric and by the ilio-inguinal 

 nerve. The anterior branch of the ilio-hypogastric nerve 

 appears near the anterior superior iliac spine, and then proceeds 

 medially under cover of the external oblique aponeurosis, which 

 it pierces near the lateral border of the sheath of the rectus 

 abdominis. The ilio - inguinal nerve perforates the internal 

 oblique a short distance medial to the hypogastric nerve and at 

 a lower level. It becomes superficial by passing through the 

 subcutaneous inguinal ring. 



Care must be taken when defining the inferior margin of the 

 muscle to preserve its relations to the spermatic cord, and not 

 to injure the muscular fasciculi which it gives to the cremaster 

 muscle. 



Aponeurosis of internal oblique 

 Reflex inguinal ligament 



M. obliquus internus 



Inguinal 

 ligament 

 Falx aponeur- 

 otica inguinalis 

 Cord covered by 

 cremaster 

 Subcutaneous 

 inguinal ring 



Cord covered by 

 external sper- 

 matic fascia 



Fascia of Scarpa 



FIG. 96. Dissection of the Inguinal Region. 

 The aponeurosis of the external oblique is turned down. 



M. Obliquus Internus Abdominis (Fig. 92). The internal 

 oblique muscle arises (i) from the lateral half of the ab- 

 dominal grooved surface of the inguinal ligament ; (2) from 

 the intermediate line of the anterior two-thirds of, the iliac 

 crest ; (3) from the lumbar fascia. The muscular fibres 

 radiate fronrtheir origins, but their general direction is from 

 below upwards and medially. The posterior fibres ascend, and 

 are inserted into the lower borders of the cartilages of the 

 lower four ribs. Those fibres occupy the same plane as the 

 ii 14:6 



