452 THE MUSCLES AND FASCIAE 



upper surface ; from the anterior two-thirds of the middle lip of the crest of the 

 ilium, and from the posterior lamella of the lumbar fascia. From this origin the 

 fibres diverge : those from Poupart's ligament, few in number and paler in color 

 than the rest, arch downward and inward across the spermatic cord, and, becoming 

 tendinous, are inserted, conjointly with those of the Transversalis, into the crest 

 of the os pubis and pectineal line, to the extent of half an inch, forming what is 

 known as the conjoined tendon of the Internal oblique and Transversalis ; those 

 from the anterior third of the iliac origin are horizontal in their direction, and, 

 becoming tendinous along the lower fourth of the linea semilunaris, pass in front of 

 the Rectus muscle to be inserted into the linea alba ; those which arise from the 

 middle third of the origin from the crest of the ilium pass obliquely upward and 

 inward, and terminate in an aponeurosis, which divides opposite the linea semilunaris 

 into two lamellae, which are continued forward, in front and behind the Rectus 

 muscle, to the linea alba, the posterior lamella being also connected to the cartilages 

 of the seventh, eighth, and ninth ribs ; the most posterior fibres pass almost 

 vertically upward, to be inserted into the lower borders of the cartilages of the 

 three lower ribs, being continuous with the Internal intercostal muscles. 



The conjoined tendon of the Internal oblique and Transversalis is inserted into 

 the crest of the os pubis and pectineal line, immediately behind the external 

 abdominal ring, serving to protect what would otherwise be a weak point in the 

 abdominal wall. Sometimes this tendon is insufficient to resist the pressure 

 from within, and is carried forward in front of the protrusion through the external 

 ring, forming one of the coverings of direct inguinal hernia ; or the hernia forces 

 its way through the fibres of the conjoined tendon. 



The aponeurosis of the Internal oblique is continued forward to the middle line 

 of the abdomen, where it joins with the aponeurosis of the opposite muscle at the 

 linea alba, and extends from the margin of the thorax to the os pubis. At the outer 

 margin of the Rectus muscle, this aponeurosis, for the upper three-fourths of its 

 extent, divides into two lamellae, which pass, one in front and the other behind 

 the muscle, enclosing it in a kind of sheath, and reuniting on its inner border at 

 the linea alba ; the anterior layer is blended with the aponeurosis of the External 

 oblique muscle ; the posterior layer with that of the Transversalis. Along the 

 lower fourth the aponeurosis passes altogether in front of the Rectus without any 

 separation. 



Relations. By its external surface, with the External oblique, Latissimus 

 dorsi, spermatic cord, and external ring ; by its internal surface, with the Trans- 

 versalis muscle, the lower intercostal vessels and nerves, the ilio-hypogastric and 

 the ilio-inguinal nerves. Near Poupart's ligament it lies on the fascia transversalis, 

 internal ring, and spermatic cord. Its lower border forms the upper boundary of 

 the spermatic canal. 



The Cremaster muscle is a thin muscular layer, composed of a number of 

 fasciculi which arise from the middle of Poupart's ligament at the inner side of 

 the Internal oblique, being connected Avith that muscle, and also occasionally with 

 the Transversalis. It passes along the outer side of the spermatic cord, descends 

 with it through the external abdominal ring upon the front and sides of the cord, 

 and forms a series of loops which differ in thickness and length in different subjects. 

 Those at the upper part of the cord are exceedingly short, but they become in 

 succession longer and longer, the longest reaching down as low as the testicle, 

 where a few are inserted into the tunica vaginalis. These loops are united 

 together by areolar tissue, and form a thin covering over the cord and testis, the 

 fascia cremasterica. The fibres ascend along the inner side of the cord, and are 

 inserted by a small pointed tendon into the crest of the os pubis and front of the 

 sheath of the Rectus muscle. 



It will be observed that the origin and insertion of the Cremaster is precisely 

 similar to that of the lower fibres of the Internal oblique. This fact affords an easy 

 explanation of the manner in which the testicle and cord are invested by this 

 muscle. At an early period of foetal life the testis is placed at the lower and back 



