MUSCLES OF THE TRUNK. 303 



wall, and the fleshy portion of the small obli(iue muscle, which forms the anterior 

 wall. 



Its inferior {external) or cutaneous orifice, also named the inguinal or external 

 ahdoniinal ring, is much larger than the superior (internal). Pierced in the 

 aponeurosis of the great oblique, in the angle formed by the union of the internal 

 border with the posterior border of tlie aponeurosis, this opening is oval in 

 form, directed obliijuely backwards and inwards, which permits it to be described 

 as having two lips or pillars, and two extremities or commissures. 



The pillars, distinguished into anterior and posterior, are composed of the 

 arciforra fibres from the aponeurosis of the great obIi(iue muscle. 



The commissures, internal and external, result from the union of the two 

 pillars at their extremities. The internal is limited by the prepubic tendon of 

 the abdominal muscles. 



The superior {internal) or peritoneal orifice of the inguinal canal, is situated 

 in front of, and directly opposite to, the crural ring. It is a simple dilatable slit, 

 comprised, like the canal itself, between the crural arch and the small oblique 

 muscle. Not well defined at its extremities, this opening includes the neck of 

 the vaginal sheath. 



4. Small or Internal Oblique Muscle of the Abdomen (Obliquus 

 Abdominis Internus) (Figs. 163, 17' ; 176, 6). 



Synonyms. — Ilio-abdominalis — Girard. 



Situation — Composition. — Situated beneath the preceding, which exactly covers 

 it, this muscle is, like it, composed of a fleshy and aponeurotic portion. 



Form, Structure, Position, and Attachments of the muscular portion. — The 

 muscular portion is very thick, triangular, and flabelliform, and occupies the 

 region of the flank. Its superior border is united, by a thick, yellow, elastic 

 production, to the aponeurosis of the latissimus dorsi, and a peculiar small 

 muscle, named by the Germans the retractor costcB {i-etractor of the last rib), 

 which we consider as a dependency of the small oblique muscle. Its posterior 

 border is slightly raised, and lies against the crural arch, from which it separates, 

 inwardly, to form the inguinal canal. Its anterior and inferior border is convex, 

 irregular, and thinner than the other portions of the muscle, and is continuous 

 witli the aponeurosis. All the fibres entering into the composition of this 

 muscular portion are spread like a fan, and leave the external angle of the ilium 

 and the external fourth of the crural arch, to be directed, the posterior fibres 

 backwards and inwards, the middle fibres downwards, and the anterior fibres 

 forwards to reach the antero-inferior border of the muscle. 



Form, Stnccture, and Attachments of the Aponeurosis. — The aponeurosis is 

 irregularly triangular, and formed of nacrous-looking fibres, which are directed 

 like tlie muscular fibres, and cross in X fashion the aponeurotic fibres of the external 

 obliiiue. It succecids the antero-inferior border of the muscular portion, and is 

 separated, superiorly, into several digitations which reach the internal face of the 

 last asternal cartilages. Throughout the whole extent of its internal border it is 

 fixed to the white line. 



Relations. — Externally, with the external oblique. The aponeui'oses of the 

 two muscles, which are merely superposed outwardly, are blended inwardly in 

 80 intimate a manner, that it might be considered their respective fasciculi were 



