3iQ THE ABDOMINAL VISCERA. 



tissue, are especially numerous at the lower end of the tube. A few of 

 the smallest which are found in the immediate neighbourhood of the 

 opening into the stomach are situate almost wholly in the substance of 

 the mucous membrane. 



Next to the submucous coat the mucous membrane is bounded by 

 longitudinally disposed plain muscular fibres which, imperfect above, 

 form a continuous layer towards the lower end of the tube {nwscularis 

 mucoscc-). 



Duplicity of the oesophagus in part of its extent, without other abnormality, 

 has been recorded (Blaes. quoted by Meckel). 



The hlood-vcsKi-ls of the oesophagus have for the most part a longitudinal 

 arrangement ; hjmphdticx are foimd in both the submucous and mucous coats, a 

 certain amount of l.>^nphoid tissue also being present in the latter. The nei-rcs 

 form a gangliated jilexus between the two layers of the muscular coat, as in 

 other iDarts of the alimentary canal. 



THE ABDOMINAL VISCEEA. 



As that part of the digestive canal which is found beneath the dia- 

 l^hragm, and consists of the stomach and intestines, is situated within 

 the cavity of the abdomen, and occupies, together with the liver (the 

 secretion of which it receives), by far the greater part of that cavitv, 

 the general topographic relations of the abdominal viscera may here be 

 briefly exjjlained. 



THE ABDOMEIT. 



The abdomen is the largest cavity in the body, and is lined by an 

 extensive and complicated serous membrane, named the peritoneum. 



It extends from the diaphragm above to the levatores ani muscles 

 below, and is subdivided into two parts : an upper and larger part, ihe 

 ahdomcn, properly so called ; and a lower part, named the 2)elvic cavitij. 

 The limits between the abdominal and pelvic portions of the cavity are 

 marked by the brim of the pelvis. 



The enclosing walls of this cavity are formed principally of muscles 

 and tendons which have been already described. They are strengthened 

 internally by a layer of fibrous tissue lying between the muscles and the 

 peritoneum, the different parts of which are described under the names 

 of fascia transversalis, fascia iliaca, and anterior lumbar fascia. These 

 walls are pierced by several apertures, through which are transmitted 

 the great vessels and some other parts, such as the several diaphragmatic 

 apertures for the aorta, vena cava, and oesophagus, and the femoral 

 arches and inguinal canals. In the median fibrous substance of the 

 anterior wall lies the umbilical cicatrix. The cavity of the pelvis is 

 also lined with strong fascire, and partially by peritoneum, and at its 

 lower part are the apertures for the transmission of the rectum and 

 the genito-urinary passages. 



Regions. — For the purpose of enabling reference to be made 

 to the situation and condition of the contained organs, the abdomen 

 jyroper has been artificially subdivided into certain regions, the bounda- 

 ries of which are indicated by lines drawn upon the surfiice of the body 

 (fig. 243). Thus, two horizontal lines drawn round the body divide the 



