392 CLINICAL APPLIED ANATOMY. 



straighten and therefore approximate to Poupart's ligament and 

 close the canal, thus having almost a sphincter-like action. 



Posteriorly, that is deeply, there is found in the outer half 

 of the canal the fascia transversalis, whilst in the inner half 

 both fascia transversalis and -conjoined tendon are seen, and 

 in front of the latter at the most internal part is the triangular 

 fascia. 



The roof of the canal is formed by the arching fibres of the 

 internal oblique and transversalis muscles, while the floor is 

 really a groove produced by the fusion of the fascia transversalis 

 with the posterior part of Poupart's ligament. 



The congenital pouch of peritoneum having passed the whole 

 length of the inguinal canal, emerges through the superficial 

 (or external) abdominal ring. This again is no true " ring," 

 being a triangular opening bounded by an inner and an outer 

 pillar, derived from the aponeurosis of the external oblique 

 muscle, and below by the crest of the os pubis. Of the two 

 pillars, the inner is flat, and is attached to the front of the 

 symphysis pubis, while the outer is rounded and is inserted 

 into the spine of the os pubis. The size of this slit in the 

 external oblique varies in different individuals. 



Except in very stout adults or young infants the superficial 

 ring can be palpated by a finger placed directly over it, immedi- 

 ately above the crest of the os pubis, a fact which is not usually 

 fully recognised. By invaginating the scrotum until the pubic 

 spine is felt, the tip of the finger may be readily made to enter 

 the ring, and if the manoeuvre is carried out with care, no pain 

 need be occasioned to the patient. There are two facts which 

 may be gleaned from this method of examination; one, the 

 approximate size of the superficial ring, a knowledge of which 

 is not of much practical moment as it has but little bearing 

 upon hernia; the other, whether there is any protrusion 

 descending the inguinal canal and impinging upon the top of 

 the examining finger, a matter of considerable moment in the 

 diagnosis between an inguinal and a femoral hernia. 



In the female, the spine of the os pubis may be defined by 



