268 



THE FIFTH DAY. 



[chap. 



body cavity which contain the lungs extending them- 

 selves ventrally round the outside of the pericardial 

 cavity. This process is illustrated by Fig. 88, taken 



Fia. 88. 



SP.c. 



Section through an Advanced Embryo of a Rabbit to 



SHEW HOW THE PERICARDIAL CaVITT BECOMES SUR- 

 ROUNDED BT THE Pleural Cavities. 



hi. heart, pc. pericafclial cavity, pl.p. pleural cavity. Ig. lung. 

 al. alimentary tract, ao. dorsal aorta. cK. notoohord. rp. 

 rib. |«i. sternum, sp.c. spinal cord. 



from an embryo rabbit. The two dorsal sections of the 

 body cavity (p/^.p.) finally extend so as completely to 

 envelope the pericardial cavity (pc), remaining how- 

 ever separated from each other below by a lamina ex- 

 tending from the ventral wall of the pericardial cavity 



