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 
Her ---- 
Fic. 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 
