Chap. VII] 



MUSCULAR TISSUE 



107 



the abdominal viscera. Thus it follows that the action of the 

 diaphragm is of assistance in expelling the foetus from the uterus, 

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

 contents from the stomach in vomiting. 



Muscles of the abdomen. — The 

 chief muscles of the abdomen are : (1) 

 external oblique, (2) internal oblique, 

 (3) rectus abdominis, and (4) trans- 

 versalis. 



External oblique. — The strongest 

 and most superficial of the abdominal 

 muscles is the external oblique. It 

 arises from the outer surface of the 

 eight lower ribs. The fibres incline 

 downward and forward and terminate 

 in the broad aponeurosis, which, meet- 

 ing its fellow of the opposite side in the 

 linea alba, covers the whole of the front 

 of the abdomen. The lowest fibres of 

 the aponeurosis are gathered together 

 in the shape of a thickened band, which 

 extends from the anterior superior spi- 

 nous process of the ilium to the pubic 

 bone, and forms the well-known and 

 important landmark, the inguinal liga- 

 ment, more commonly known as Pou- 

 part's ligament from the anatomist 

 who first described it. 



Internal oblique. — The internal oblique muscle lies just beneath 

 the external oblique. It arises from the inguinal ligament, the 

 outer crest of the ilium, and slightly from the lumbar fascia.^ 



' The lumbar fascia springs from the vertebral column in three layers : — 



(1) Outer, or posterior. 



(2) Middle. 



(3) Inner, or anterior. 



(1) The outer layer begins at the spinous process of the lumbar and sacral 

 vertebrae. It is attached above to the last rib, and below to the outer tip of the 

 iliac crest and the ilio-lumbar ligament. 



(2) The middle layer starts from the transverse processes of the lumbar vertebrse 



(3) The inner layer starts from the front of the bases of the same processes. 

 The fascia resulting from the combination of these three layers gives rise to the 



internal oblique and transversalis muscles. 



Fig. 7S. — Rectus Abdomi- 

 nis AXD Obliquds Internus 

 OF Right Side. (Gerrish.) 



