Description of Plate 5. 

 Lung of Necturus maculatus. 



Fig. 5. Relation of nuclei and protoplasm to group of cells in an 

 island, x 350. 



Fig. 6. A single cell forming an island, x 250. 



Fig. 7. Cell boundaries crossing over nuclei of neighboring cells, 

 x 250. 



Fig. 8. Projection drawing of two cells from figure 7, showing 

 relation of cell boundaries to nucleus and to two un- 

 derlying capillaries, x 250. 



