1909. ] SUBDIVISIONS OF THE BODY-CAYVITY IN BIRDS. 223 
the pericardium. Their lateral walls are formed by the post- 
pulmonary septum, and the median partition between them is the 
ventral mesentery or falciform ligament. 
Text-fig. 33. 
Jeti (OF es spt. 
Abd.c -7 fe 
Ph. rs: 
Bhp. sp ryy.s. 
Diagrammatic plan showing the subdivisions of the celom in a bird in 
longitudinal section. 
Text-fig. 34. 
Ppl.spe. . Ing. 
va Puy. as. / 
Chick of 17 days’ incubation bisected longitudinally a little to the left of the 
middle line; seen trom the right side. 
These figures show likewise that the pleural cavities persist 
even in the adult; though they tend to get somewhat obscured 
by the fusion here and there of the adjacent layers of pleural 
epithelium, and the development of connective-tissue strands 
across the cavities. 
