DISSECTION OF THE ABDOMEN. 303 



portion of intestine or mesentery sometimes passes into the inguinal 

 canal, or outwards into the scrotum, constituting an inguinal or a 

 scrotal hernia. 



The Prepubic Artery (Plate 44). This vessel arises from the femoral 

 artery at the brim of the pubis, forming a short common trunk with 

 the deep femoral branch. It crosses to the edge of the internal 

 oblique, and divides into the external pudic and posterior abdominal 

 arteries. The former enters the inguinal canal at a point internal 

 to the internal abdominal ring. The latter passes behind the ring, 

 and crosses it on the inner side. Both branches have already been 

 followed, but the relation of the posterior abdominal artery to the 

 ring should now be specially noted, as, in consequence of its position, 

 an incision for the relief of a strangulated hernia must be made 

 outwards to avoid wounding the vessel. 



The Spermatic Cord is formed at the internal abdominal ring by the 

 meeting of the vas deferens with the vessels and nerves of the testicle. 

 These constituents of the cord, together with a small amount of con- 

 nective tissue and some non-striped muscular tissue (the cremaster 

 internus), are invested by peritoneum which forms part of the tunica 

 vaginalis propria. The entire cord has the form of a long triangle, 

 of which the apex lies at the internal abdominal ring, and the base at 

 the testicle. The anterior edge and both surfaces of the cord are free, 

 while the posterior edge is attached to the wall of the inguinal canal 

 through the continuity between the tunica vaginalis propria of the 

 cord and the tunica vaginalis reflexa of the canal. The vas deferens 

 ascends on the inner side of the cord in a special narrow fold of the 

 tunica vaginalis propria, and at the internal abdominal ring it will 

 be seen turning inwards to enter the pelvis. The vessels and nerves 

 of the cord are to be left undisturbed, so that they may be followed 

 to their source at a later stage. 



The Cremaster Muscle (Plate 44). The fibres of this muscle are 

 now seen at their orgin from the iliac fascia, where they are close to the 

 muscular fibres of the internal oblique. They pass into the inguinal 

 canal, where, separating but remaining connected by intermediate 

 areolar tissue, they constitute the cremasteric covering of the cord and 

 testicle. When the muscle contracts it twitches the testicle upwards 

 by shortening the spermatic cord. 



THE CAVITY OF THE ABDOMEN. 



Boundaries of the Cavity. — The abdomen is the largest of the visceral 

 cavities of the body. It is placed behind the thorax, from which it is 

 separated by the diaphragm ; posteriorly it is directly continuous with 

 the cavity of the pelvis ; laterally and inferiorly it is enclosed by muscu- 



