FASCLE OF THE PEEINJEUM. 259 



tare, and forms in cases of oblique hernia one of the coverings of the 

 tumour. 



The fascia iliaca, more limited in extent, but stronger than the fascia 

 transversalis, lines the back part of the abdominal cavity, and covers not 

 only the muscle from which it derives its name, but also the psoas. 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, be- 

 coming 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 vertebrae ; and finally it becomes 

 blended with the fascia which covers the diaphragm and forms the liga- 

 inentum arcuatum externum. The external iliac vessels lie in front 

 of this part of the iliac fascia. To the outer side of those vessels, the 

 fascia turns forwards to be connected with Poupart's ligament and the 

 fascia trausversalis, as already described ; to the inner side of the femoral 

 vein it is attached to the ilio-pectineal line, where also the fascia lata, being 

 traced upwards, is found to terminate ; and between these two points, 

 namely, behind the femoral vessels, it continues downwards over the margin 

 of the pelvis, forming the back part of the sheath of those vessels, in the 

 same manner as its fore part is formed by the fascia transversalis. 



The psoas parvus is closely connected with the iliac fascia, by means of 

 an expansion of its tendon. 



At the back part of the abdomen is the aponeurosis of the quadratus 

 lumborum muscle, forming the anterior layer of the lumbar aponeurosis ; 

 this, together with the posterior and middle layers, has been already 

 described along with the transversalis muscle, with the aponeurotic origin of 

 which they are all connected. 



FASCLE OF THE PERINEUM. 



As a knowledge of the disposition of the fasciae of the perinssum and 

 pelvis assists the comprehension of the attachments and relations of the 

 muscles of those regions, the fasciae will here be first described. 



Superficial Fascia. In the posterior half of the perinseum the sub- 

 cutaneous fat is continued deeply into the ischio-rectal fossa, the pyramidal 

 space intervening between the obturator fascia and the levator ani muscle, 

 lu the anterior half of the perinseum, beneath the subcutaneous fat, is placed 

 a special layer of fascia, continuous with the dartos, the proper superficial 

 perinceal fascia, sometimes called fascia of Colles. This fascia is bound down 

 on each side to the margin of the pubic arch as far back as the ischial tuber- 

 osity ; posteriorly, along a Hue from the ischial tuberosity to the central 

 point of the perinseum, it turns round the posterior margin of the trans- 

 versus perinsei muscle to join the subpubic fascia, to be presently described. 

 From its deep surface likewise, an incomplete septum in the middle line 

 dips down to the urethra and passes forwards into the scrotum. It thus 

 happens that air blown in beneath the proper perinseal fascia on one side 

 passes forwards and distends the scrotum to a certain extent on that side ; it 

 may then penetrate to the other also, and if injected with sufficient force 

 may reach the front of the abdomen and travel upwards beneath the super- 

 ficial fascia ; but it neither passes backwards to the posterior half of the 

 perinseum nor down upon the thighs. The same course is followed by urine 

 or matter extravasated beneath the proper peiinseal fascia. 



8 9 



