1909. ] SUBDIVISIONS OF THE BODY-CAVITY IN BIRDS. 221 
pulmo-hepatic recess of that side. Text-fig. 33, p. 223, shows very 
diagrammatically the divisions of the ccelom in the adult. bird in 
longitudinal vertical section. Text-fig. 34 is of a chick 17 days 
after the beginning of incubation, bisected longitudinally a little 
to the left of the middle line, and seen from the right side. The 
arrangement of the septa is the same as in the adult fowl but is 
shown more clearly, since in the latter the mesenteries are often 
loaded with fat. The gizzard is seen enclosed in the post-hepatic 
septum just dorsal to the attachment of the latter to the ventral 
body-wall, and in front of the umbilicus. Dorsally the septum is 
seen formed first by that part of the median mesentery which 
supports the spleen in the left pulmo-hepatic recess (see also 
text-fig. 31), and then by the post-pulmonary septum which is 
Text-fig. 31. 
=. 
SH 
Li 
NS Yj 
Ye 
(Nw 
Transverse section of a chick of 13 days’ incubation, through the connection between 
the posterior part of the post-pulmonary septum and the mesentery of the 
liver and gizzard; seen from behind. 
itself united dorsally with the vertebral column by means of the 
median dorsal mesentery (see text-fig. 30, p. 219). By this time the 
air-sacs have increased so much in size, as completely to obliterate 
all the connective tissue of the post-pulmonary septum which 
at first surrounded and separated them from each other; and 
the walls of the adjacent air-sacs have become closely applied to 
each other, As a result of this, the post-hepatic septum appears 
in the figure to be completed dorsally by the posterior wall of the 
posterior intermediate air-sac together with the fused anterior 
