OF THE ABDOMEN. 361 



\vhich divides at the outer border of the Rectus muscle into two lamelhe, which are 

 continued forward, in front and behind this muscle, to the linea alba, the posterior 

 lamella being also connected to the cartilages of the seventh, eighth, arid 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 ab- 

 dominal ring, serving to protect what would otherwise be a weak point in the ab- 

 dominal 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 conjoined tendon is sometimes 

 divided into an outer and an inner portion the former being termed the ligament 

 of Hesselbaclt ; the latter, the ligament of Henle. 



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 sheat^i, 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. Where the aponeurosis ceases to split, and passes altogether in front 

 of the Rectus muscle, a deficiency is left in the sheath of the muscle behind ; this 

 is marked above by a sharp lunated margin having its concavity downward. 

 This is known as the semilunar fold of Douglas. 



Relations. By its external surface, Avith 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 trans- 

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

 boundary of the inguinal canal. 



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

 fasciculi which arise from the inner part of Poupart's ligament, where its fibres 

 are continuous with those of the Internal oblique 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 eremasterica. 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 

 part of the abdominal cavity, but during its descent toward the scrotum, which 

 takes place before birth, it passes beneath the arched fibres of the Internal oblique. 

 In its passage beneath this muscle some fibres are derived from its lower part 

 which accompany the testicle and cord into the scrotum. It occasionally happens 

 that the loops of the 'Cremaster surround the cord, some lying behind as well as in 



