OF THE ABDOMEN. 453 



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 

 front. It is probable that under these circumstances the testis, in its descent, 

 passed through instead of beneath the fibres of the Internal oblique. 



In the descent of an oblique inguinal hernia, which takes the same course as 

 the spermatic cord, the Cremaster muscle forms one of its coverings. This muscle 

 becomes largely developed in cases of hydrocele and large old scrotal hernia. No 

 such muscles exist in the female, but an analogous structure is developed in those 

 cases where an oblique inguinal hernia descends beneath the margin of the Internal 

 oblique. 



Dissection. Detach the Internal oblique in order to expose the Transversalis beneath. This 

 may be effected by dividing the muscle, above, at its attachment to the ribs ; below, at its con- 

 nection with Poupart s ligament and the crest of the ilium ; and behind, by a vertical incision 

 extending from the last rib to the crest of the ilium. The muscle should previously be made 

 tense by drawing upon it with the fingers of the left hand, and if its division is carefully effected, 

 the cellular interval between it and the Transversalis, as well as the direction of the fibres of the 

 latter muscle, will afford a clear guide to their separation ; along the crest of the ilium the cir- 

 cumflex iliac vessels are interposed between them, and form an important guide in separating 

 them. The muscle should then be thrown forward toward the linea alba. 



The Transversalis muscle (Fig. 294), so called from the direction of its fibres, is 

 the most internal flat muscle of the abdomen, being placed immediately beneath 

 the Internal oblique. It arises by fleshy fibres from the outer third of Poupart's 

 ligament ; from the inner lip of the crest of the ilium for its anterior three- 

 fourths ; from the inner surface of the cartilages of the six lower ribs, interdigitating 

 with the Diaphragm ; and by the middle layer of the lumbar fascia (posterior apon- 

 i-u'rosis of the muscle itself) from the tips of the transvere processes of the lumbar 

 vertebrae. The muscle terminates in front in a broad aponeurosis, the lower fibres 

 of which curve downward and inward, and are inserted, together with those of 

 the Internal oblique, into the lower part of the linea alba, the crest of the os 

 pubis and pectineal line, forming Avhat is known as the conjoined tendon of the 

 Internal oblique and Transversalis. Throughout the rest of its extent the apon- 

 eurosis passes horizontally inward, and is inserted into the linea alba ; its upper 

 three-fourths passing behind the Rectus muscle, blending with the posterior lamella 

 of the Internal oblique ; its lower fourth passing in front of the Rectus. 



Relations. By its external surface, with the Internal oblique, and the inner 

 surface of the cartilages of the lower ribs ; by its internal surface, with the fascia 

 transversalis, which separates it from the peritoneum. Its lower border forms the 

 upper boundary of the spermatic canal. 



Dissection. To expose the Rectus muscle, open its sheath by a vertical incision extending 

 from the margin of the thorax to the os pubis. and then reflect the two portions from the surface 

 of the muscle, which is easily done, excepting at the lineae transversae, where so close an 

 adhesion exists that the greatest care is requisite in separating them. Now raise the outer edge 

 of the muscle, in order to examine the posterior layer of the sheath. By dividing the muscle in 

 the centre, and turning its lower part downward, the point where the posterior wall of the 

 sheath terminates in a thin curved margin will be seen. 



The Rectus abdominis is a long flat muscle, which extends along the whole 

 length of the front of the abdomen, being separated from its fellow of the opposite 

 side by the linea alba. It is much broader, but thinner, above than below, and 

 arises by two tendons, the external or larger being attached to the crest of the os 

 pubis, the internal, smaller portion interlacing with its fellow of the opposite side, 

 and being connected with the ligaments covering the front of the symphysis pubis. 

 The fibres ascend, and the muscle is inserted by three portions of unequal size 

 into the cartilages of the fifth, sixth, and seventh ribs. Some fibres are occasion- 

 ally connected with the costo-xiphoid ligaments and side of the ensiform cartilage. 



The Rectus muscle is traversed bv tendinous intersections, three in number. 



