EXPLANATION OF THE PLATES. 



PLATE XL VII. 



Fig. 1. The pleural surface of a portion of Lung magnified 30 

 diameters. This figure conveys an accurate idea of 

 the form and great abundance of the air cells. 



Fig. 2. Pleural surface of a section of Lung showing the dis- 

 tribution of the vessels of the first of the three 

 orders of sizes mentioned in the text. 



Fig. 3. Ditto of Lung magnified 100 diameters. The vessels 

 in this are not injected, but are represented as they 

 appeared in a section which had become slightly 

 dried. 



