362 THE MUSCLES AND FASCIA 



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. 

 The Cremaster muscle is found only in the male, but almost constantly in the fe- 

 male a few muscular fibres may be seen on the surface of the round ligament, 

 which correspond to this muscle, and in cases of oblique inguinal hernia in 

 the female a considerable amount of muscular fibre may be found covering 

 the sac. 



Dissection. Detach the Internal oblique in order to expose the Trnnsversalis 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 Transyersalis, 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 inward toward the linea alba. 



The Transversalis muscle (Fig. 220), 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 from the lumbar fascia, which may be regarded as the pos- 

 terior aponeurosis of the muscle. (See page 342.) 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 what is known as 

 the conjoined tendon of the Internal oblique and Transversalis. Throughout the 

 rest of its extent the aponeurosis 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, the lower inter- 

 costal nerves, and the inner surface of the cartilages of the lower ribs ; by its in- 

 ternal surface, with the fascia transversal! 8, which separates it from the periton- 

 eum. Its lower border forms the upper boundary of the inguinal 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 linese 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. The upper portion, at- 

 tached principally to the cartilage of the fifth rib, usually has some fibres of inser- 

 tion into the anterior extremity of the rib itself. Some fibres are occasionally 

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



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



