THE PERITONEUM. 23 



their precise situation by the peritoneum ; which extends from 

 them to the contiguous surface of the cavity, and adheres where 

 it is in contact, so as to produce this effect. 



Fig. 132.* 



Other viscera, which are not in close contact, but movable 

 to a distance from the posterior surface of the abdomen, are 

 covered by this membrane, which is extended to them from 

 the surface ; and this extended portion forms an important part 

 of the connexion between the viscus and the cavity in which 

 it lies. This connecting part is called Mesentery, when it thus 

 passes to the small intestines ; Mesocolon, when it goes to the 

 colon, one of the larger intestines ; and Ligament, when it passes 

 to some of the other viscera. 



The peritoneum is a complete but empty sac, which is fixed 

 in the abdomen anterior to the viscera. The anterior portion 

 of this sac forms the lining to the anterior and lateral parts of 

 the surface of the abdomen : the posterior portion covers the 

 viscera, and forms the mesentery, mesocolon, and ligaments 

 above described. 



It necessarily follows that the mesentery and the other simi- 

 lar processes are mere plaits or folds of the sac, which invests 

 the viscera ; and that they must consist of two lamina ; and as 

 the blood-vessels, nerves, and absorbents, are all posterior to 



* Diagram representing a transverse section of the abdomen, in the lumbar 

 region, a, Umbilicus, b, A lumbar vertebra, c, Kidneys, d, Ascending 

 colon, e, Small intestine. /, Descending colon, g, Inferior vena cava. 

 ft, Aorta, i, Left mesocolon, k, Mesentery. I, Right mesocolon. 



