rilE PEIUTOyFA'M 



955 



until it reaches the descending colon. This it covers, as a rule, in front and on 

 the sides, though occasionally, as shown in the diagram (fig. 561), it forms a 

 meso-colon. Then it passes over the hodies of tlie vertehra? with the large vessels 

 upon them, and leaves the back of the a])domen to run forward to enclose the 

 termination of the small intestine, returning again to the si)ine. The two layers 

 thus form the mesentery, liaving jjetwirn tliem the terminal branches of the sujx'- 

 rior mesenteric vessels. It tlien passes over the right half of the i)osterior abdom- 

 inal wall, covering the ascending colon in front, and at the sides only, vmless there 

 be a meso-colon, and then passes on to the side and front of the abdomen to the 

 point from whi('h it was first traced. 



In tracing the peritoneum in a section of the Ixxly (fig. 562) opposite the 

 stomacii, on a level with the first lumbar vertel)ra, its course becomes more com- 

 plicated and difficult to follow. 



In the section already given tlie peritoneum as a sim]»l(' closed sac can l)e 

 readily conceived; but at the level now exposed the serous membrane has ])een so 

 introverted that there appears to be two sacs, one leading from tlie other. The 

 lesser is indeed but a diverticulum or l)ulging from the greater, and the manner of 

 its formation is exi)laincd on page 1002. These two sacs are called the greater 

 and the lesser sacs of the peritoneum. They communicate through a narrow 

 strait or neck, the foramen of W'inslow. The lesser sac or cavity is discovered 



Fiu. 562. — Transverse Section of the Abdomex at the Level of the Foramen 



OF WlNSLOW. 



GASTRO-HEPATIC OMENTUM 



GASTRO-SPLENIC 

 OMENTUM 



bt'bind tlie stomach, so that on first opening the abdomen no trace of it is to l)e 

 seen. It extends downwards between the layers of the great onnaitum (though this 

 part of the lesser sac is always obliterated by adhesion in the adult ). It extends 

 upwards to the under surface of the liver, and is limited behind l)y the i>osterior 

 abflominal wall; and below, Ix'hind the great omentum, by the transverse meso- 

 colon. Its disi)osition on vertical si'ction is shown in fig. 563. 



The foramen of Winslow is situated just l>elow the liver; it looks forwards and 

 towards tlie right, and will readily admit one or two fingers. It is bounded above 

 by the caudate lobe of the liver; below, by the duodenum and hepatic vessels; 

 behind, by the vena cava; and in front by the gastro-hepatic or lesser omentum, 

 containing the structures passing to and from the liver. 



Starting at the foramen of Winslow, tlic lesser sac Avill be found to turn to the 

 left. 



If ni>\v the ])critoncuni be vii-wcd in a transverse section of the body at the 

 level named, viz., through the lirst lumbar vertebra, it will be found that the sec- 

 tion has probaldy passed through the foramen of W'inslow ( lig. 5(i2). Starting at 

 the front of the abdomen and going to the right, tlie peritoneum is seen to line the 

 anterior abdominal wall, to pass over the side of the abdomen, and to cover the 

 front of the right kidney; it then extends on to the vena cava, when it becomes a 

 l»art of the lesser sac; then along the back of the lesser sac, over the aorta and i)an- 



