S24 MUSCLES OF THE ABDOMEN. 



ftiiterior wall of its sheath, causes the fonnation of corresponding- transversa 

 folds during- its contraction, and may enable the separate parts of the muscle to 

 act on different portions of the abdominal wall. The pyramidalis muscle 

 strengthens the inferior part of the rectus. 



Lining fascia of the abdomen.— On the inner surface of the wall 

 of the abdomen is a membranous structure which lines the visceral 

 aspect of the deepest stratum of muscles ; it is divisible into two 

 principal parts, the fascia transversalis and fascia iliaca. 



The fascia transversalis is named from its position on the deep 

 surface of the transversalis muscle. It is strongest in the lower part 

 of the abdomen, where the muscular and tendinous supi)ort is somewhat 

 weaker. Followed upwards from this situation, the transversalis fascia 

 becomes gradually less strong, and bej'ond the margin of the ribs it 

 forms a thin covering for the under surface of the diaphragm. Along 

 the inner surface of the iliac crest, between the iliacus and trar-aversalis 

 muscles, the fascia is attached to the periosteum. For about two inches 

 inwards from the anterior superior iliac spine, it is closely connected 

 "with the posterior sm-face of Poupart's ligament, and is there directly 

 continuous with the fascia iliac. At this place also, and to the same 

 extent it is attached to the fascia lata. About midway between the 

 iliac spine and the pubis, the external iliac artery and vein, as they pass 

 out into the thigh, intervene between the fascia transversalis and the 

 fascia iliaca, and from this point to the edge of Gimbcrnat's ligament 

 the fascia transversalis is prolonged downwards under the crural arch, 

 and over the artery and vein, forming the anterior portion of the 

 funnel-shaped femoral sheath. As this prolongation of the fascia passes 

 under Poupart's ligament, it is strengthened by a dense band of fibres 

 (the deep crural arch) which arches over the vessels, and is inserted 

 into the pubic crest and pectineal line behind the conjoined tendon 

 of the transversalis and internal oblique. It includes beneath it, internal 

 to the vessels, a space between Gimbernat's ligament and the vein, suflR- 

 ciently large to admit the point of the little finger ; this is called the 

 crural rwg, and is the space through which femoral hernia descends. 

 About half way between the anterior superior iliac spine and the sym- 

 physis pubis, and about half an inch above Poupart's ligament, the 

 spermatic cord in the male, or the round ligament in the female, pierces 

 the fascia transversalis. The opening thus made is called the internal 

 or deep abdominal rincj ; the fascia above and internal to it is thin, but 

 below and external to it is firm and thick, and forms a distinct crescentic 

 margin, over which the cord or round ligament passes ; from the borders 

 of the opening a delicate funnel-shaped covering, the 'mftmdihuliform 

 fascia, is prolonged downwards on the emerging structure, and forms in 

 cases of ol)]ique hernia one of the coverings of the tumour. 



The fascia iliaca, stronger than the fascia transversalis, lines the 

 back part of the abdominal cavity, and covers the iliacus and psoas 

 muscles. The densest portion of its fibres is stretched transversely from 

 the iliac crest, over the margin of the psoas muscle to the brim of the 

 pelvis, where it is intimately blended with the periosteum. Superiorly, 

 this membrane, becoming much weaker, is connected internally with 

 the sacrum, and by small and distinct processes with the intervertebral 

 substances and the neighbouring margins of the lumbar vertebra3 ; and 

 finally it becomes blended with the fascia which covers the diaphragm 

 and torms the ligamentum arcuatum externum. The external iliac 



