382 CLINICAL APPLIED ANATOMY. 



be opened, and that muscle pulled aside, so that when allowed 

 to return it covers the incision in the posterior wall of the 

 sheath, or access may be gained by separating the external 

 oblique, internal oblique, and transversalis muscles in the 

 direction of their fibres which decussate with each other. In all 

 cases it is important to bear in mind that the outer edge of 

 the rectus usually extends in the adult to within two inches of 

 the anterior superior iliac spine. 



DISEASES OF THE PERITONEUM. 

 ACUTE PERITONITIS. 



Acute peritonitis is usually the result of infection which has 

 spread from some viscus which is invested by the visceral or 

 abuts against the parietal layer of the membrane. In the female 

 the orifices of the Fallopian tubes allow infection to spread from 

 the genital passages. In some cases peritonitis results from 

 blood-borne infection, and it may also follow penetrating wounds 

 of the sac. The extension of the serous membrane into the 

 dome of the diaphragm renders the sac liable to penetration by 

 wounds of the lower part of the thorax, and its extension around 

 the rectum and along the upper third of the posterior vaginal 

 wall exposes it to injury in these situations. The membrane 

 may also be infected along a patent funicular process. 



The most vulnerable part of the visceral layer is that which 

 invests the small intestine and appendix. The pelvic portion is 

 more resistant to infection. It is exceptional for infection to 

 spread through the parietal portion of the greater sac from 

 without, but this sometimes happens, particularly in the region 

 of the diaphragm. The lymphatic channels are better developed 

 in this situation. The parietal portion of the lesser sac is liable 

 to infection from the subjacent pancreas. 



The great absorptive power of the peritoneum accounts for the 

 rapidity with which toxic symptoms arise in peritonitis. The 

 area of the membrane is said to be equal to that of the whole 

 integument of the body, and it is looked upon as a large 

 lymphatic space, although it is doubtful if its direct connexion 



