400 ABDOMEN 



it is fixed to the vertebral column by a series of fibrous 

 arches which bridge over the lumbar arteries. Superiorly, it 

 thickened to form the band termed the medial lumbo- 

 costal arch. Inferior ly, the fascia expands so as to cover 

 both the psoas and the iliacus ; at the same time it becomes 

 much denser and thicker and is called the fascia iliaca. The 

 fascia iliaca has important connections and relations. The 

 external iliac vessels lie upon it, whilst the femoral nerve 

 lies behind it. The genito-femoral nerve pierces it, and comes 

 into relation with the external iliac artery. Laterally, it is 

 firmly fixed to the crest of the ilium ; medially, it sweeps 

 over the psoas, and is attached to the brim of the pelvis 

 minor. The attachments mentioned can be easily demon- 

 strated if the fascia is divided in the vertical direction, over 

 the iliacus, a short way to the lateral side of the psoas, and 

 is then reflected medially and laterally. It is very loosely 

 attached to the subjacent muscles, so that the fingers can 

 readily be passed behind it, first in a lateral and then in a 

 medial direction. Note that no perceptible fascial partition 

 dips backwards from it between the psoas and iliacus. 



The inferior connections of this fascia have already 

 been studied (Vol. I., p. 240). On the lateral side of the iliac 

 vessels it has been seen to become continuous with the fascia 

 transversalis, and, at the same time, to be attached to the 

 inguinal ligament ; whilst behind the femoral vessels it is 

 carried downwards into the thigh, to form the posterior wall 

 of the femoral sheath. 



Surgical Anatomy. The attachments of the ilio-psoas fascia are of 

 high surgical importance. When an abscess forms in connection with the 

 lumbar vertebrae the pus readily passes downwards within the psoas sheath, 

 and in certain cases is conducted behind the inguinal ligament so as to 

 point in the thigh. It cannot enter the pelvis minor owing to the attach- 

 ment of the fascia iliaca to the ilio-pectineal line. 



Dissection. The muscles should now be cleaned and their 

 attachments defined ; but, while that is being done, certain 

 points must be attended to. The medial portion of the fascia 

 iliaca must be preserved, in order that its relation to the pelvic 

 fascia may be afterwards made out. In the case of the psoas major 

 muscle, care must be taken not to injure (i) the sympathetic 

 trunk, which lies along its anterior margin ; (2) the genito- 

 femoral nerve, which runs downwards on its anterior surface ; 

 (3) the ilio-inguinal nerve, and the lateral cutaneous nerve of 

 the thigh, which appear at its lateral border ; and (4) the femoral 

 nerve, which lies in the interval between it and the iliacus muscle. 

 In the case of the quadratus lumborum, bear in mind that the 



