THE PERITONEUM 353 



of contact would be about twice as wide, including about all of the fleshy rim. This fact is of 

 clinical importance, with reference to auscultation and percussion, and penetrating wounds. 

 The cupola of the diaphragm extends as far forward as a plane through the sixth intercostal 

 space to the right of the heart. 



There is no wall between the abdominal and pelvic cavities. The line of de- 

 marcation here is the terminal line (Linea terminalis) or brim of the pelvis; it is 

 formed by the base of the sacriiin, the ilio-pectineal lines, and the anterior borders 

 of the pubic bones. 



The muscular walls are lined by a layer of fascia, tlistinguished in different 

 parts as: (1) the diaphragmatic fascia; (2) the transversalis fascia; (3) the iliac 

 fascia; (4) the deep layer of the hmibo-dorsal fascia. 



The subperitoneal or extraperitoneal connective tissue (Tela subserosa) unites 

 the fascia and peritoneum. It is composed of areolar tissue, more or less loaded 

 with fat according to the condition of the subject, except over the diaphragm. It 

 sends laminae into the various peritoneal folds. 



The peritoneum, the serous membrane which lines the cavity, will be described 

 later. 



The abdominal walls are pierced in the adult by five apertures. These are: 

 the three openings in the diaphragm which transmit the aorta, posterior vena cava, 

 and the oesophagus; the inguinal canals, w^hich contain the spermatic cord or the 

 round ligament (in female carnivora). In the fa'tus there is the umbilical opening 

 also. 



The cavity contains the greater part of the digestive and urinary organs, part 

 of the internal generative organs, numerous nerves, blood-vessels, lymph vessels and 

 glands, ductless glands (spleen and adrenal bodies), and certain foetal remains. 



For topographic purposes the abdomen is divided into nine regions by imagin- 

 ary planes.^ Two of these planes are sagittal, and two are transverse. The 

 sagittal planes cut the middles of the inguinal (Poupart's) ligaments; the transverse 

 planes pass through the last thoracic and fifth lumbar vertebrae, or the lower end 

 of the fifteenth rib and the external angle of the ilium respectively. The transverse 

 j)lanes divide the abdomen into three zones, one behind the other, viz., epigastric, 

 mesogastric, and hypogastric: these are subdivided by the sagittal planes as in- 

 dicated in the subjoined table. 



Left parachondriac Xiphoid Right parachondriac 



Left lumbar Umbilical Right luml)ar 



Left iliac Prepubic Right iliac. 



Other useful regional terms are: sublumbar, diaphragmatic, inguinal. The 

 first two require no explanation. The inguinal regions (right and left) lie in front 

 of the inguinal (Poupart's) ligament. The flank is that part of the lateral wall 

 which is formed only of soft structures. The depression on its upper part is termed 

 the paralumbar fossa. 



THE PERITONEUM" 



The peritoneum is the thin serous membrane which lines the abdominal and 

 (in part) the pelvic cavity, and covers to a greater or less extent the viscera con- 

 tained therein. In the male it is a completely closed sac, but in the female there 

 are two small openings in it ; these are the abdominal orifices of the Fallopian tubes, 

 which at their other ends communicate with the uterus, and so indirectly with the 

 exterior. The peritoneal cavity is only a potential one, since its opposing walls 



' This method of division, although long in use, is of very little value for accurate descrip- 

 tion. It is mentioned here chiefly because agreement on a more useful topographic method has 

 not been arrived at. 



" Only a general account of the arrangement of the peritoneum is given in this section, since 

 a detailed description cannot be understood wthout a knowledge of the viscera concerned. 

 23 



