THE BODY-CAVITIES 345 



soon taken up by the caudal elongation of the stomach. Oblitera- 

 tion of the cavity of the omentum by fusion of its walls takes 

 place at its caudal end. (Broman.) 



Spaces corresponding to the omental cavities are also formed 

 on the left side of the body, but they are of much less extent. 

 (See Fig. 196.) The communication of these spaces with the 

 greater peritoneal cavity is not, however, shut off as on the right 

 side. However, a secondary and later fusion of the left lobe 

 of the liver with the lateral body-wall, and of the gizzard with 



rBr 



Her 



FIG. 195. Reconstruction of the omental space of a chick embryo of 154 

 hours from the right side. (After Broman.) 



Bomaj., Bursa omenti majoris. Bomin., Bursa omenti minoris. Du., 

 Duodenum. Giz., Gizzard. Her., Hiatus communis recessum. oe., (Esoph- 

 agus. rBr., Right bronchus. Rpedx., Right pneumato-enteric recess. 



the ventral body-wall does isolate a portion of the peritoneal 

 cavity from the remainder on the left side. Into this the pneu- 

 mato- and hepato-enteric cavities of the left side open; however, 

 it is obvious that this space is not analogous to the omental 

 spaces on the right. 



Origin of the Spleen. The spleen arises as a proliferation from 

 the peritoneum clothing the left side of the dorsal mesentery 

 just above the extremity of the dorsal pancreas. This prolifera- 

 tion forms the angle of a cranio-caudal fold of the dorsal mesen- 

 tery which is caused by the displacement of stomach and intestine 



