ABDOMINAL WALL 



385 



form of a thin membrane called the external spermatic fascia. In defining 

 this the blade of the knife must not be used. Work entirely with the 

 handle. The thin layer of deep fascia which is spread over the muscular 

 part of the external oblique muscle must also be removed. In doing this 

 it is not necessary to carry the knife in the direction of the fleshy fasciculi. 

 Indeed, the muscle can best be cleaned by carrying the knife at right angles 

 to the general direction of the fibres. In front, the deep fascia will be seen 

 to blend with the aponeurosis of the muscle, along 

 the line of junction between the tendinous and fleshy 

 fibres. The slips of origin of the external oblique 

 muscle from the eight lower ribs must each be care- 

 fully defined. 



M. Obliquus Abdominis Externus (Ex- 

 ternal Oblique). The external oblique 

 muscle arises by eight pointed processes or 

 digitations from the outer surfaces and lower 

 borders of the eight lower ribs (Fig. 142). 

 Of these, the upper three interdigitate with 

 the digitations of the serratus anterior, and 

 the latissimus dorsi interdigitates with the 

 lower three. From this origin the fibres 

 proceed downwards and forwards with vary- 

 ing degrees of obliquity. The posterior 

 fibres have a nearly vertical direction, and 

 are inserted into the anterior half of the 

 lateral lip of the crest of the ilium. The 

 superior fibres are almost horizontal, and the 

 intermediate fibres are directed obliquely 

 downwards and forwards, and all end in a 

 strong aponeurosis called the aponeurosis 

 of the external oblique. 



Superiorly the aponeurosis of the external 

 oblique is very thin, and is carried forwards ^W 



to be attached to the xiphoid process. It 

 is from this part that the pectoralis major FlG - 143- Crest of 



, . ~, c . 7- / 7 A. the Ilium as seen 



derives fibres of origin. Inferwrly the from above (semi . 



aponeurosis is folded upon itself to form diagrammatic), with 

 the inguinal ligament which is attached Attachments of 

 laterally and superiorly to the anterior ^ scl< 

 superior spine of the ilium, and medially 

 and inferiorly to the tubercle of the pubis. Between the upper 

 and lower attachments the aponeurosis lies in front of the 

 rectus, and is inserted into the linea alba and into the front of 

 the os pubis. 



In connection with this aponeurosis note that it is broadest 



VOL. i 25 



