900 



THE ORGANS OF DIGESTION. 



its peritoneal covering by the splitting of the two posterior layers of the latter 

 fold. 



In addition to tracing the peritoneum vertically, it is necessary to trace it hori- 

 zontally. If this is done below the transverse colon, the circle is extremely simple, 

 as it includes only the greater sac of the peritoneum (Fig. 488). Above the level 

 of the transverse colon the arrangement is more complicated, on account of the 

 existence of the two sacs. 



Starting from the linea alba, below the level of the transverse colon, and 

 tracing the continuity in a horizontal direction to the right, the peritoneum covers 

 the internal surface of the abdominal wall almost as far as the anterior border of 

 the Quadratus lumborum muscle ; it encloses the caecum, and is reflected over the 

 sides and anterior surface of the ascending colon, fixing it to the abdominal wall, 

 from which it can be traced over the kidney to the front of the bodies of the 

 vertebrae. It then passes along the mesenteric vessels to invest the small intes- 



Passes through foramen of 

 Winslow. 



^Lesser amentum. 



Fio. 488. The reflections of the peritoneum, as seen in a vertical section of the abdomen. 



tine, and back again to the spine, forming the mesentery, between the layers of 

 which are contained the mesenteric blood-vessels, nerves, lacteals, and glands. 

 Lastly, it passes over the left kidney to the sides and anterior surface of the descend- 

 ing colon, and, reaching the abdominal wall, is continued along it to the middle 

 line of the abdomen. 



Above the transverse colon (Fig. 489) the peritoneum can be traced, forming 

 the greater and lesser cavities, and their communication through the foramen of 

 WmsloAV can be demonstrated. Commencing in the middle line of the abdomen, 

 the membrane may be traced lining its anterior wall, and sending a process back- 

 ward to encircle the obliterated umbilical vein (the round ligament of the liver), 

 forming the falciform or longitudinal ligament of the liver. Continuing its course 



