STUDIES ON THE MAMMARY GLAND 431 
The lining of the milk-ducts in the adult virgin human has 
been described by von Ebner as consisting of a single layer of 
epithelial cells. Starling and Lane-Claypon (’06) also reported 
a single layer of epithelium surrounding the ducts in virgin rab- 
bits. Rein (’82) divided the duct in rabbits of two months into 
Fig. 9 Drawn from a cross-section of a secondary milk-duct of a female al- 
bino rat of nine weeks. Zenker’s fixation; Weigert’s iron-hematoxylin stain. 
Drawn with the aid of a camera lucida. c.t., connective tissue; 7./., inner or 
glandular layer of epithelium; o./., outer or myo-epithelial layer. > 800. 
Fig. 10 Drawn from a section through the terminal branches of a collateral 
duct of a female albino rat of nine weeks. Zinker’s fixation; Weigert’s iron- 
hematoxylin stain. Drawn with the aid of a camera lucida. c.t., connective 
tissue. The cross-sections through the six terminal parts show in general a 
single layer of epithelium. An occasional flattened nucleus represents the outer 
or myo-epithelial layer. > 800. 
