364 



MUSCLES AND FASCIA. 



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

 from the margin of the thorax to the pubes, 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 downwards, the point where the posterior wall of the sheath 

 terminates in a thin curved margin will be seen. 



Fig. 233. A Transverse Section of the Abdomen in the Lumbar Region. 



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 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 oppo- 

 site side, and being connected with the ligaments covering the symphysis pubis. 

 The fibres ascend vertically, and the muscle, becoming broader and thinner at 

 its upper part, is inserted by three portions of unequal size into the cartilages 

 of the fifth, sixth, and seventh ribs. Some fibres are occasionally connected 

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



The Eectus muscle is traversed by a series of tendinous intersections, which 

 vary from two to five in number, and have received the name linese transverse?. 

 One of these is usually situated opposite the umbilicus, and two above that point ; 

 of the latter, one corresponds to the ensiform cartilage, and the other, to the 

 interval between the ensiform cartilage and the umbilicus ; there is occasionally 

 one below the umbilicus. These intersections pass transversely or obliquely 

 across the muscle in a zigzag course ; they rarely extend completely through 

 its substance, sometimes pass only halfway across it, and are intimately adherent 

 to the sheath in which the muscle is inclosed. 



The Eectus is inclosed in a sheath (Fig. 233) formed "by the aponeuroses of 

 the Oblique and Transversalis muscles, which are arranged in the following 

 manner. When the aponeurosis of the Internal Oblique arrives at the margin 

 of the Eectus, it divides into two lamella?, one of which passes in front of the 

 Eectus, blending with the aponeurosis of the External Oblique; the other, 

 behind it, blending with the aponeurosis of the Transversalis ; and these, join- 

 ing again at its inner border, are inserted into the linea alba. This arrange- 

 ment of the fascia? exists along the upper three-fourths of the muscle ; at the 

 commencement of the lower fourth, the posterior wall of the sheath terminates 

 in a thin curved margin, or falciform edge, the concavity of which looks down- 

 wards towards the pubes ; the aponeuroses of all three muscles passing in front 

 of the Eectus without any separation. The Eectus muscle, in the situation 



