548 ABDOMEN 



anterior lamella of the lumbar fascia, and posteriorly by the 

 middle lamella of the lumbar fascia (Fig. 148, p. 395). 



Fascia covering the Psoas and Iliacus. This is one con- 

 tinuous aponeurotic sheet. Above the level of the crest of the 

 ilium, where it is merely in relation to the psoas, it is thin and 

 narrow. Here it is attached laterally to the fascia covering 

 the quadratus lumborum, whilst medially it is fixed to the 

 spine by a series of fibrous arches which bridge over the 

 lumbar arteries. Superiorly, it has been seen to form the 

 thickened band termed the arcus lumbo-costalis medialis. 

 Below the fascia expands so as to cover both the psoas and 

 the iliacus, and at the same time it becomes much denser 

 and thicker. Here it receives the name of the fascia iliaca, 

 and presents most important connections. The external iliac 

 vessels lie upon it, whilst the femoral nerve lies behind it. 

 The lumbo-inguinal nerve pierces it, and comes into relation 

 with the external iliac artery. Laterally it is firmly fixed to 

 the crest of the ilium, whilst medially it sweeps over the 

 psoas, and is attached to the brim of the small pelvis. 

 These attachments can be easily demonstrated by dividing 

 it in the vertical direction, over the iliacus, a short way to 

 the lateral side of the psoas. 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 (p. 183). 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 these 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 owing to the attachment 

 of the fascia iliaca to the ilio-pectineal line. 



Dissection. The muscles should now be cleaned and their attachments 

 defined ; but, in doing this, certain points must be attended to. The medial 

 portion of the fascia iliaca must be carefully preserved, in order that its 

 relation to the pelvic fascia may be afterwards made out. In the case of 



