THE PERITOXE I 'U. 



975 



terior lamella covers a large part of the posterior abominal wall, and its original 

 line of vertebral attachment gets displaced to the left ; it joins the diaphragm and 

 forms the liy. phreno-lien-ih 1 . suspensory ligament of the spleen. Below it be- 

 comes fused to the upper layer of the transverse mesocolon and to the trans- 

 verse colon (Fig. 603). These two contiguous layers, i. e. the posterior layer of 

 the mesogastrium and the upper layer of the transverse mesocolon, may present 

 a fissure at birth in many mammals. During early infancy in the human species 

 they form a single lamella with a deposit of fat (Fig. 603). In adult life no trace 

 of the extra layer is seen. 



There are then three types of relation of the posterior layer of the great 

 omentum to the transverse mesocolon : foetal, where they are separate (Fig. 602); 

 infantile, where they are fused into one layer (Fig. 603); and adult, where all 

 trace of this layer has disappeared and the posterior lamella of the great omen- 

 turn seems to enclose the transverse colon (Fig. 606). 



Diaphragm 



Liver 



Stomach 



Greater curvature 



Anterior lamella of greater omentum 

 Posterior lamella of greater omentum 



Transverse colon 



Greater omentum 



Letter omentum 



Pancreas 



Transverse mesocolon 

 Duodenum 



Mesentery 



SmaU intestine 



FIG. 602. Diagram to illustrate the development of the bursa omentalis, cavity of the great omentum or 

 lesser sac. Fcetalstage. *. Lesser sac. (Hertwig.) 



The lesser sac of peritoneum (bursa omentalis) is still continuous with the 

 greater sac or general peritoneal cavity, something like the two cavities of an 

 hour-glass, only the upper cavity (lesser sac) is comparatively small and bent 

 down behind the other. In Fig. 603 the cavity behind the stomach is connected 



Diaphragm 



Liver 



Stomach 



Greater curvaturi 



Pusierior lamella of greater omentu 

 Transverte colon 



Greater omentum 



Lesser omentum 



Part of omentum enclosing pancreas 



TViJ >/.-->. r.. l' 



Duodenum 



Small intestine 



FIG. 603. Development of bursa omentalis. Infantile stage. Great omentum covers the intestines and has 

 fused with the transverse mesocolon. Pancreas is free of peritoneum posteriorly. (Hertwig.) 



with the larger cavity in front of it by means of a foramen to the right of the 

 lesser omentum. It is the foramen of Win*l.f>>i\ and is to be found just under 

 the hilus (the black spot on a bean) of the liver to the right side of the neck of 

 the gall-bladder. 



After childhood the cavity of the lesser sac descending into the great omen- 

 tum is obliterated and the four layers are fused into an omcntal plate. 



