THE THIGH 239 



upon the vessels, and fuses with their coats about the 

 level of the distal limit of the fossa ovalis. It should be 

 noticed that the sides of the funnel -shaped sheath do 

 not slope equally towards one another. The lateral border 

 of the sheath is nearly vertical in its direction, whilst the 

 medial wall proceeds very obliquely distally and laterally. 

 If the dissection has been successfully performed, the 

 lumbo-inguinal nerve should be seen piercing the lateral 

 wall of the sheath, whilst the great saphenous vein and 

 some lymph vessels perforate its anterior wall. Further, if 

 the subject is spare and the fasciae well marked, the dissector 

 will in all probability notice that the anterior wall of the 

 sheath, in its proximal part, is strengthened by some transverse 

 fibres which pursue an arched course across it. To those 

 fibres the name of deep femoral arch is given, in contra- 

 distinction to the term superficial femoral arch, which is 

 sometimes applied to the inguinal ligament. The deep 

 femoral arch springs from the deep surface of the inguinal 

 ligament about its middle, then traverses the front of the 

 sheath, and expanding somewhat, is attached by its medial 

 extremity to the pectineal line of the pubic bone behind the 

 lacunar ligament. 



Constitution of the Femoral Sheath. The sources from 

 which the femoral sheath is derived, and the manner in 

 which it is formed, must next be considered. The considera- 

 tion entails the study of some of the structures concerned in 

 the construction of the abdominal wall, and it is possible 

 that the dissection of the abdomen will not be in a sufficiently 

 advanced state for their examination. 



A small portion of the medial part of the interval 

 between the inguinal ligament and the hip bone is filled 

 up by the lacunar ligament. Immediately to the lateral 

 side of the lacunar ligament the femoral vessels, enclosed 

 within the femoral sheath, enter the thigh from the 

 abdominal cavity, whilst still more laterally the interval is 

 occupied by the ilio-psoas muscle. Three nerves also find 

 their way into the thigh through the interval, viz., the lumbo- 

 inguinal nerve, which passes distally in the femoral sheath ; 

 the femoral (O.T. anterior crural) nerve, which occupies the 

 interval between the psoas and iliacus muscles ; and the lateral 

 cutaneous nerve of the thigh, which runs behind the inguinal 

 ligament, close to its iliac attachment (Fig. in). 



