284 MUSCLES AND FASCIAE. 



of Poupart's ligament, being attached to the groove on its upper surface ; from the 

 anterior two-thirds of the middle lip of the crest of the ilium, and from the lumbar 

 fascia. From this origin, the fibres diverge in different directions. Those from 

 Poupart's ligament, few in number and paler in color than the rest, arch down- 

 wards and inwards across the spermatic cord, to be 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 the conjoined tendon of the Internal oblique and Trans- 

 versalis; those from the anterior superior iliac spine are horizontal in their 

 direction, whilst those which arise from the fore part of the crest of the ilium 

 pass obliquely upwards and inwards, and terminate in an aponeurosis, which is 

 continued forwards to the linea alba. The most posterior fibres ascend almost 

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

 four 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 abdo- 

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

 abdomen. Sometimes this tendon is insufficient to resist the pressure from within, 

 and is carried forward in front of the protrusion through the external ring, form- 

 ing one of the coverings of direct inguinal heoaia. 



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 pubes. At the 

 outer margin of the Eectus muscle, this aponeurosis, for the upper three-fourths 

 of its extent divides into two lamellas, which pass, one in front and the other 

 behind it, inclosing 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 Transversalis 

 muscle, fascia transversalis, internal ring, and spermatic cord. Its lower border 

 forms the upper boundary of the spermatic canal. 



Dissection. The Internal oblique should now be detached in order to expose the Transver- 

 salis beneath. This may be effected by dividing the muscle, above, at its attachment to the 

 ribs ; below, at its connection 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 pre- 

 viously 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 direc- 

 tion of the fibres of the latter muscle, will afford a clear guide to their separation ; along the 

 crest of the ilium the circumflex iliac vessels are interposed between them, and form an im- 

 portant guide in separating them. The muscle should then be thrown forwards towards the linea 

 alba. 



The Transversalis muscle (fig. 165), 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, its anterior two-thirds, from 

 the inner surface of the cartilages of the six lower ribs, interdigitating with the 

 Diaphragm, and by a broad aponeurosis from the spinous and transverse processes 

 of the lumbar vertebras. The lower fibres curve downwards, and are inserted, 

 together with those of the Internal oblique, into the crest of the os pubis and 

 pectineal line, forming what was before mentioned as the conjoined tendon of these 

 muscles. Throughout the rest of its extent the fibres pass horizontally inwards, 

 and near the outer margin of the Rectus terminate in an aponeurosis, which 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 obliq le, the inner surface 



