64 ANATOMY FOR NURSES. [CHAP. VI. 



anatomist who first described it, Poupart's ligament. Just 

 above this ligament, and near the pubic bone, is an oblique 

 opening which transmits the spermatic cord in the male, or the 

 round ligament in the female. This opening, called the ex- 

 ternal abdominal ring, is usually the seat of hernia. 



The internal oblique muscle lies just beneath the external 

 oblique. Its fibres run upwards and forwards, and end for the 

 most part in a broad aponeurosis. At the outer border of the 

 rectus muscle this aponeurosis divides into two layers, one passing 

 before, the other behind, that muscle : they reunite at its inner 

 border in the linea alba, and thus form a sheath for the rectus. 



The transversalis muscle lies beneath the internal oblique; 

 the greater part of its fibres have a horizontal direction, and 

 extend forward to a broad aponeurosis in front. 



The rectus is a long, flat muscle, consisting of vertical fibres 

 situated at the fore part of the abdomen, and enclosed in the 

 fibrous sheath formed by the aponeurosis of the internal oblique. 

 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. 



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 perpendicularly, in the middle line, from the 

 ensiform portion of the sternum to the pubis. It is a little 

 broader above than below, and a little below the middle it is 

 widened into a flat circular space, in the centre of which is sit- 

 uated the cicatrix of the umbilicus. 



The abdominal muscles perform a threefold action. When 

 acting from both pelvis and thorax as fixed points they com- 

 press the abdominal viscera by constricting the cavity of the 

 abdomen, in which action they are much assisted by the descent 

 of the diaphragm. (See below.) By .these means they give 

 assistance in expelling the foetus from the uterus, the faeces 

 from the rectum, the urine from the bladder, and its contents 

 from the stomach in vomiting. When the pelvis and spine are 

 the fixed points the abdominal muscles raise the diaphragm by 

 pressing on the abdominal viscera, draw down the ribs, compress 

 the lower part of the thorax, and assist in expiration. Again, 



