The Abdominal iMuscles. 



277 



Linea 



M. obliquus interims abdominis 



M. obliquus exteriius abdominis 



322. Transverse section through the abdominal 

 wall above the linea semicircularis [Douglasi] 



(after W. Braune). 



Cutis 



Fascia transversalis 



M. obliquus externus abdominis ' 



323. Transverse section through the abdominal 

 wall below the linea semicircularis [Douglasi] 



(after W. Braune). 



M. rectus abdomiuis (see Figs. 321 and 324). Form: flat, oblong-quadrangular, above 

 broader and thinner, below narrower and thicker. Position: on the anterior surface of the 

 abdomen close to the linea alba. In front it is covered by the anterior leaf of the vagina m. 

 recti abdominis; behind it lies in its upper two thirds on the posterior leaf of the vagina m. 

 recti, in the lower third directly upon the fascia transversalis. Origin: anterior surface of the 

 5th 7tii costal cartilage, of the proc. xiphoideus and of the lig. costoxiphoideum. Insertion: 

 its fibres run downward, parallel to one another, close to the linea alba. In its upper half it 

 is interrupted by three intercalated tendons, inscriptiones tendineae ; the uppermost, usually 

 incomplete, corresponds approximately to the inferior margin of the thorax, the lowermost runs 

 transversely at the level of the navel, and the middle one, between these two, in the same direction ; 

 these intermediate tendons oiten do not go entirely through the thickness of the muscle ; they 

 are very intimately connected with the anterior leaf, but loosely with the posterior leaf of the 

 rectal sheath. The number and extent of these tendons varies: usually there is an incomplete 

 one below the navel at the level of the linea semicircularis | DouglasiJ. Below, the muscle fibers 

 converge and are attached by a strong flat tendon to the ramus superior oss. pubis and to the 

 anterior surface of the symphysis ossium pubis ; the fibers of the tendons are very much inter- 

 woven. Action: it draws the thorax downward and bends the spinal column forward; when 

 the thorax is fixed it elevates the pelvis. Single sections of the muscle can contract separately. 

 Innervation: rami anteriores [nn. intercostales] of the nn. thoracales Y XTI. 



