MUSCLES OF THE TRUNK. 



243 



Fig. 116. 



_ Form, Structure, and Attachments of the aponeurosis. — The aponeurosis is 

 irregularly triangular, and formed of nacrous- looking fibres, which are 

 directed like the muscular fibres, and cross 

 in X fashion the aponeurotic fibres of 

 the external oblique. It succeeds the an- 

 tero-inferior border of the muscular por- 

 tion, and is separated, superiorly, into 

 several digitations which reach the in- 

 ternal face of the last asternal cartilages. 

 Throughout the whole extent of its in- 

 ternal border it is fixed to the white line. 



Relations. — This muscle is covered 

 by the external oblique. The aponeuroses 

 of the two muscles, which are merely 

 superposed outwardly, are blended in- 

 wardly in so intimate a manner that it 

 might be thought their respective fasci- 

 culi were woven into each other. The 

 small oblique covers the great straight 

 and the transverse muscles. 



Action. — This muscle, a congener of 

 the preceding, compresses the abdominal 

 viscera, depresses the last ribs, and causes 

 the flexion, either direct or lateral, of the 

 vertebral column. 



The retractor muscle of ike last rib. — 

 This small muscle, flattened on each side, 

 and triangular in form, originates by 

 aponeurotic fibres from the summits of 

 the first two or three transverse processes 

 of the lumbar region. It terminates on 

 the posterior border of the last rib. 

 Covered by the last digitation of the pos- 

 terior serratus and by the great oblique, 

 it covers in turn the transverse muscle of 

 the abdomen. In contracting it draws j, „,i, oTtliTgreat oblique; 2, 



the last rib backwards, and fixes it in Muscular portion of the small oblique 



that position, in order to permit the ex- 

 piratory action of the internal intercostal 

 muscles. It therefore plays the same 

 part, in regard to these muscles, that the 

 scalenus does to the external intercostal 

 muscles (Fig. 106, 17). 



5. Great Rectus Muscle of the Abdomen. 

 (Figs. 105,20; 116,3.) 



Synonyms. — Sterno-pubialis — Girard. {Bec- 

 tus abdominis — Percivall.) 



MUSCLES OF THE INFERIOR ABDOMINAL 

 REGION. 



3, Rectus" abdominis ; 3', Transverse 

 muscle; 4, Flat tendon by which the 

 four abdominal muscles are inserted 

 into the pubis ; 5, Inguinal ring ; 6, 

 Its anterior pillar ; 7, Its posterior 

 pillar ; 8, Its external commissure ; 9, 

 Internal commissure; 10, Posterior 

 border of the great oblique aponeu- 

 rosis; 11, Internal crural aponeurosis; 

 12, Strip of the great oblique aponeu- 

 rosis turned downwards to show the 

 origin of Poupart's ligament , 14, 

 Traces of the umbilicus. 



Situation — Extent — Form — Structure. 



This is a wide and powerful muscular band, extending from the sternum 



to the pubis, included between the aponeurosis of the internal oblique and 

 that of the transverse muscle, narrower at its extremities than in its middle 

 portion, and divided by numerous transverse and zig-zag fibrous inter- 



