THE MAMMARY GLAND. 



445 



cubical, cylindrical (Kolessnikow) ; small polyhedral (Langer) ; 

 and prismatic (Kehrer) cells. This discrepancy of opinion re- 

 ceives its explanation from the fact that the epithelial cells 



FIG. 191. Lobule of a mamma near the resting state. Numerous large pigmented cells within the 

 acini and in the interlobular flbrillar tissue. Creighton. 



have a different appearance in the various conditions interven- 

 ing between full activity and complete rest of the gland. 



Creighton has given a very satisfactory description of mam- 

 mary epithelium. He states that in the fully expanded gland 

 " the floor of an acinus in section is covered by a mosaic of 

 polyhedric epithelial cells, usually to the number of fifteen 

 or twenty, while in the larger elongated 

 acini as many as thirty may be counted. 

 The cells are usually pentagonal or hex- 

 agonal, and the corners are sometimes 

 rounded. In each cell there is a central 

 round nucleus, which colors brightly 

 with the staining fluid, and abroad fringe 

 of protoplasm, which stains less deeply." 

 The nucleus varies in its relative size, 

 generally having a diameter equal to 

 about one-third that of the entire cell. 

 " In a profile view of an acinus, the epithelium appears as a 

 circlet of oblong cells, in which the nucleus at the centre occu- 

 pies almost the entire thickness of the cell. The mammary 

 epithelial cell may therefore be described as a flattened poly- 

 hedric body, with a thickness about one-half of its breadth. 

 The substance of the nucleus is apparently homogeneous, with 



FIG. 192. Fully expanded aci- 

 nus, showing mosaic of polyhedral 

 cells. Creighton. 



