HISTOLOGY OF THE MAMMARY GLAND. 
.277 
ally find flattened polygonal cells, which by the action of a half p. c. 
solution of arg. nit. stained the protoplasm yellow or yellowish brown, 
whilst their contours were black. In all these cases the membrana pro¬ 
pria appeared as an idiocyntric membrane of connective tissue, whose 
connection with the epithelial cells could not be distinguished. The 
epithelial cells are completely isolated from the membrana propria. I 
saw the epithelial cells become detached, scales, which upon a closer 
observation appeared to be isolated epithelial cells, which had been 
attached to the membrana propria by means of a glutinous substance. 
Henle (Anatomy II., p. 46), was the first to observe and describe 
these stellate cells which belong to the membrana propria in the mam¬ 
mary gland of the human subject. Langer (Strieker Handbuch der 
Gewebelehre, 1872, p. 627), confirms Henle’s observation, and says that 
the membrana propria consists of the so-called stellate cells. Kolliker 
(Handbuch der Gewebelehre, 1867), describes the membrana propria as 
a structureless membrane; and Furstenburg (Die Milchdrtise der Kuh 
Leipsig, 1869), came to the same conclusion after investigating the 
mammary gland of the cow. Langhaus (Virchow’s Archiv., vol. 59), 
thinks that the stellate cells form no constant part of the membrana 
propria, but that it is a structureless membrane or composed of spindle- 
shaped cells. 
In order to study the structure of the membrana propria, I took 
the normal mammary gland of the cow during lactation, and investi¬ 
gated fresh preparations as well as those hardened in Muller’s fluid and 
alcohol, and stained with carmine, hematoxylin, eosin and tincture of 
iodine. I removed the epithelial layer from the membrana propria of 
some sections by penciling, others were shaken in distilled water. 
In preparations prepared in this manner the membrana propria 
appeared as a membrane composed of flattened stellate connective tis¬ 
sue cells, united by means of their processes. By a closer investigation 
I convinced myself that their projections proceeded from the central 
part of the nucleated cells not as recticulum, but are to be considered as 
striae seen in the compact, homogeneous membrane, and that these fibers 
with their stellate cells and the homogeneous membrane forms a histo¬ 
logical unit. In other alveole these striae were spindle-shaped, from 
0.003-0.012 m.m. in diameter, and 0.015 m.m. apart, and ran parallel to 
the greater diameter of the alveole. From these striae pass off processes 
which appear as fine condensations (and remind one of the recticulum), 
of the homogeneous membrane lying between the described striae. In 
the center of the stellate, and in various parts of the spindle-formed 
