NO- VII. 



THE STRUCTURE OF THE SEROUS MEMBRANES. 



A portion of the human pleura or peritoneum will be found to 

 consist, from its free surface inwards, of a layer of nucleated 

 scales, of a germinal membrane,* and of the sub-serous areolar 

 texture intermixed with occasional elastic fibres. The blood- 

 vessels of the serous membrane ramify in the areolar texture. 



There is one stratum only of the nucleated scales in the super- 

 ficial layer of the serous membrane. This layer conceals the 

 germinal membrane, which can only be detected after the re- 

 moval of the scales. 



The germinal membrane does not in general shew the lines of 

 junction of its component flattened cells. These appear to be 

 elongated in the form of ribbons, their nuclei, or the germinal 

 spots of the membrane being elongated, expanded at one ex- 

 tremity, pointed at the other, and somewhat bent upon them- 

 selves. The direction of these flattened cells and nuclei is the 

 same in any one part of the membrane, this direction being in 

 general parallel to the subjacent blood-vessels, in the neighbour- 

 hood of which they exist in greatest numbers. The germinal 

 spots are bright and crystalline, and may, or may not, according 

 to their condition, contain smaller cells in their interior. They 



* 1 stated this fact in my Paper on the Intestinal Villi, in the Ed. Phil. Journal, July 

 1822. Dr. Todd and Mr. Bowman, in their " Physiology of Man," have described the 

 same membrane in the serous texture. 



