EXPLANATION OF THE PLATES. 



PLATE XL VIII. 



Fig. 1. A section of Lung from beneath the pleural surface 

 magnified 100 diameters, injected with tallow 



Fig. 2. Casts or models of the Air Cells magnified 350 dia- 

 meters, representing the variety in size and form 

 of these cells as well as the shape and number of 

 the openings of communication. 



Fig. 3. Deep section of Lung injected with size : the majority 

 of the cells are observed to be filled with the casts 

 tipped with colouring matter : other cells may also 

 be seen without casts : these have evidently been 

 cut across, exposing to view the ciliated epithelium 

 which lines them. 



