242 THE MUSCLES. 



is continuous with the femoral aponeurosis and that of the great oblique 

 muscle. 



INGUINAL CANAL. This is an infundibuliform canal compressed on each 

 side, through which the spermatic cord and scrotal artery pass from the 

 abdomen in the male, and the external mammary vessels in the female. 



Situated on the side of the prepubic region, in an oblique direction 

 downwards, backwards, and inwards, and measuring from two to two-and- 

 a-half inches in length, this canal lies between the crural arch, which con- 

 stitutes its posterior wall, and the fleshy portion of the small oblique 

 muscle, which forms the anterior wall. 



Its inferior (external] or cutaneous orifice, also named the inguinal 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 the aponeurosis, this opening is of an oval form, 

 directed obliquely 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 

 arciform fibres from the aponeurosis of the great oblique 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. 

 (Figs. 106, 17'; 116, 2.) 



Synonyms. Ilio-abdominalis Girard. (Obliquus internus abdominis PercivaU.') 



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 great dorsal (latissimus dorsi), and a 

 peculiar small muscle, named by the Germans the retractor costce (retractor 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 with 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. 



inferiorly, with the upper border of Poupnrt's ligament. This lamina is perhaps only a 

 dependency of the subperitoneal aponenrosis ; and if so, it represents the only vestige 

 of the fascia transversals it has been p ssible to discover in Solipeds. 



