108 



ANATOMY FOR NURSES 



[Chap. VII 



Its most posterior fibres run upward and forward and are 

 inserted in the costal cartilages of the four lower ribs. At the 

 outer border of the rectus muscle the remaining muscle fibres 

 expand into a ijroad aponeurosis. This aponeurosis divides into 

 two layers, one passing before, the other behind, the rectus 

 muscle; they reunite at its inner border in the linea alba, and 

 thus form a sheath for the rectus, extending from the xiphoid 

 process to the crest of the pubes. At the lower part of the rectus 

 the posterior layer of the aponeurosis is deficient. 



Rectus abdominis. — The rectus is a long, flat muscle, consisting 

 of vertical fii)res situated at the fore part of the abdomen, and 



enclosed in the fibrous sheath formed 

 by the aponeurosis of the internal ob- 

 lique. It arises from the pubic bone, 

 and is inserted into the cartilages of 

 the fifth, sixth, and seventh ribs ; it is 

 separated from the muscle of the other 

 side by a narrow interval which is 

 occupied by the linea alba. 



Transversalis. — The transversalis 

 muscle lies beneath the internal oblique. 

 The fibres arise from the six lower costal 

 cartilages, the lumbar fascia, the crest 

 of the ilium, and the outer third of the 

 inguinal ligament. The greater part of 

 its fibres have a horizontal direction, 

 and are inserted in the linea alba and 

 the crest of the pubes. 



Linea alba. — The linea alba, or white 

 line, is a tendinous band formed by the 

 union of the aponeuroses of the two 

 oblique and transverse muscles, the 

 tendinous fibres crossing one another 

 from side to side. It extends perpen- 

 dicularly, in the middle line, from the 

 xiphoid portion of the sternum to the 

 pubes. It is a little broader above than below, and a little be- 

 low the middle it is widened into a flat, circular space, in the 

 centre of which is situated the umbilicus. 



Fig. 79. — Transversalis 

 Abdominis of Right Side. 

 (Gerrish.) 



