DISSECTING MANUAL. 



part of the fourth lumbar nerves. The first and second each 

 divide into upper and lower branches. The upper branch of 

 the first (often getting a branch from the twelfth thoracic) di- 

 vides into the ilio-hypogastric and ilio-inguinal. The lower 

 branch of the first and upper branch of the second join, form- 

 ing the genito-crural. The lower branch of the second, the 

 third, and the portion of the fourth each divide into an an- 

 terior and a larger posterior part; the anterior parts (except 

 sometimes that of the second) unite, forming the obturator; 

 the posterior parts also unite, forming the anterior crural. 

 The external cutaneous arises from the back of the posterior 

 parts of the second and third. Muscular branches to the 

 Quadratus lumborum arise from the first three or four lumbar 

 (sometimes the last thoracic) , and to the Psoas from the second 

 and third (sometimes also the first or fourth) lumbar nerves 

 near their origins. [641] 



Ilio-hypogastric. This runs through the Psoas, across the 

 Quadratus lumborum, and between the Transversalis and In- 

 ternal oblique above the iliac crest. Then piercing the Inter- 

 nal oblique just in front of the anterior superior spine it runs 

 between this and the External oblique aponeurosis, pierces 

 the latter an inch and a half above the external abdominal 

 ring and (as the hypogastric branch) supplies the adjacent skin. 

 Muscular branches supply the abdominal wall. Iliac branch (in- 

 constant) ; this descends through the abdominal wall and over 

 the iliac crest behind the iliac branch of the last thoracic, to the 

 skin on the upper and outer part of the buttock. [642] 



Ilio-inguinal. This is often fused at first with the preced- 

 ing; it runs a similar course, at a lower level, but pierces the 

 Internal oblique further forward. It then runs through the 

 external abdominal ring and supplies (cutaneous branches') the 

 abdominal wall over the symphysis, the thigh over Scarpa's 

 triangle supero-internally, and the top of the scrotum and root 

 and dorsum of the penis (mons Veneris and labium ma jus). 

 Muscular branches supply the abdominal wall. [642] 



[200] 



