210 E. CRESSWELL BABER. 



in appearance, and considerably larger than the adjacent 

 epithelial cells. Their cell-substance is finely granular, and 

 they are each provided with a single large nucleus. Some- 

 times these cells present an irregular outline, and are at the 

 same time smaller, as if the cell-substance had shrunk up 

 round the nucleus, leaving a space between it and the sur- 

 rounding structures. In other parts of the specimens, how- 

 ever, the cell-substance presents a regular rounded outline, 

 and is in contact with the neighbouring elements. The 

 nuclei of the parenchymatous cells are round or oval in shape, 

 and present a well-marked outline. They are larger than 

 those of the epithelial cells, and do not stain quite so darkly 

 with hsematoxylin. In their interior are seen* several 

 nucleoli. The parenchymatous cells are met with either 

 alone or in groups. In the latter case several frequently 

 appear to be situate in a common cavity, which they do not 

 fill out (see fig. 4). With regard to their relation to the 

 walls of the vesicles, these cells may occupy at least four 

 positions. 



1. They are found, either singly or in groups, external to 

 the vesicles, and separated from their cavity by a layer of 

 normal epithelial cells {i. e. epithelial cells as described 

 above). 



2. Other parenchymatous cells, also situate in the inter- 

 vesicular spaces, are seen to be separated from the cavity of 

 an adjoining vesicle by a layer o'i jiattened epithelial cells, 

 the latter presenting a concave surface to the parenchyma- 

 tous cells. 



3. Some parenchymatous cells are seen encroaching on 

 the layer of epithelial cells to such an extent that they are 

 only separated from the cavity of the vesicle by a thin mem- 

 brane. They lie, as it were, in a cup formed by the flattened 

 epithelial cells (see fig. 3, c). 



4. In other cases these cells are seen lying in a cup formed 

 by the epithelial cells, and in which the flattened epithelial 

 cells, or the membrane, separating the parenchymatous cells 

 from the cavity of the vesicle have given way, thus placing 

 the parenchymatous cells in direct communication with the 

 contents of the vesicle (see fig. 4, h). In this, as in all 

 other situations described, the cells may be single or several 

 together, apparently occupying a common cavity. 



Lastly, rounded cavities formed by flattened epithelial 

 cells and communicating with the cavity of a vesicle are 

 sometimes seen in an empty condition. 



The above appearances represent the diff'erent stages of a 

 process which may be summed up as follows : — The par en- 



