LUNGS 



381 



thickening is that the branches of the intrapulmonary bronchus 

 form comparatively narrow canals separated by mesodermic tissue. 



Lutcrnl border 



Lateral linmi'lii unit 

 i In if 



FIG. 287. Thalassochelys caretfa. (After A. Malani.) 



Moreovei 1 , a distinction of the bronchi into portions serving merely 

 for the passage of air and into respiratory portions becomes 



, /,t,-</ bronchi in 

 ant* rior part n/i 

 /\ 



}'eii1 ral secoml- 

 ii i'il bronchi 



Swollen termina- 

 tion of main 

 bronchus 



Dorsal bonlt.i' Dorsal secondary bronchi 

 with alveoli 



FIG. 288. LUNG OF Alligator mississipiensis. 



The bronchus enters the lung some distance from the anterior end. 



(After A. Malani. ) 



gradually more marked, and thus eventually leads to the condition 

 seen in Birds and Mammals. Both ontogenetically and phylo- 



