ABDOMINAL REGION. 203 



pillar of the inguinal canal, and externally gives attachment to 

 the posterior fibres of the internal oblique. Posteriorly it contacts 

 the sartorius and pectin eus muscles, and the crural vessels, 

 embracing those parts in a sort of arch, hence its name. Its 

 superior border at its external half is attached to the lumbo-iliac 

 aponeurosis ; while its middle is confounded with the external 

 surface of the sartorius and iliacus. Inside the attachments 

 of the pectineus and psoas parvus, it forms, with the anterior 

 border of the pubis, the iliacus and sartorius, a triangular open- 

 ing called the crural ring, through which the crural vessels pass 

 out of the abdomen. The inferior border is continuous with the 

 femoral and great oblique aponeuroses. 



Inguinal Canal. 



The Inguinal Canal is infundibuliform and compressed 

 laterally ; through it pass the spermatic cord and external 

 pudic artery of the male, and mammary vessels of the female. 

 It is situated obliquely between the crural arch, which is its 

 posterior, and the internal oblique muscle, which forms 

 its anterior wall. The external orifice is called the external 

 abdominal ring, and is larger than the internal, being oval in 

 form and directed backwards and inwards. It presents two 

 pillars and two extremities or commissures. The pillars, 

 anterior and posterior, are merely the edges or lips of the 

 aperture, and are formed by the arciform fibres of the 

 aponeurosis of the external oblique muscle, the posterior one 

 being assisted by Poupart's ligament. The commissures, external 

 and internal, are formed by the union of the pillars, the latter 

 being limited by the prepubian tendon. The peritoneal or 

 internal abdominal ring, the internal orifice of the canal, is 

 situated in front of the crural ring. It is a mere dilatable cleft 

 between the crural arch and the internal oblique, and but 

 indifferently marked at its extremities. 



OBLIQUUS ABDOMIXIS IXTERNUS. 



(Ilio-abdomino.Hs. ) 

 (PL. III. -2!X) 



Situated under the externus, on the postero-lateral and inferior 

 aspects of the abdomen, its fibres expanding downwards, it is, 

 like the externus, fleshy and aponeurotic ; the fleshy portion is 



