Chap. xxviii.] ORGANS OF RESPIRATION. 



221 



membrane contains numerous elastic fibres, and 

 on the free surface is covered with a layer of endo- 

 thelium. 



In some instances (guinea-pig) the pleura pulmo- 

 nalis contains bundles of non-striped muscular tissue. 



Fig. 128. From a Section through the Lung of Cat, stained with Nitrate 

 of Silver. 



a, An inf undibulum or alveolar duct in cross section ; 6, groups of polyhedral 

 cells lining one part of tlie infuudibuluiu, the rest being lined with flattened 

 transparent epithelial scales ; c, the alveoli lined with flattened epithelial 

 scales ; here and there between them is seen a polyhedral granular epithelial 

 cell. (Atlas.) 



The lobes of the lung are separated from one 

 another by large septa of connective tissue the liga- 

 menta pulmonis. 



291. The terminal bronchi contain no cartilage 



