4 MILK [i 



smallest of the ductlets are clustered several alveoli. 

 Of these milk-cisterns there are four, one above each 

 teat. They thus act, as their name indicates, as 

 cisterns for supplying the teats with milk. 



The alveoli or pouches above mentioned are sur- 

 rounded by a structureless membrane (tunica propria), 

 the internal surface of which is thickly covered with 



FIG. 3. HALF DIAGRAMMATIC VIEW OF A SECTION THROUGH A LOBULE OF 

 THE MAMMARY GLAND (after Klein, Atlas of Histology, Plate 40, Fig. 1). 

 Magnified 45 diameters, a, A duct dividing into two branches ; b, b, b, 

 connective tissue surrounding and going between the ultimate pouches of 

 the gland ; c, c, c, the pouches or alveoli of the gland, the dots representing 

 the cells lining them. 



epithelial cells (see Figs. 5 and 6). The mem- 

 brane is further covered with a system of capillary 

 blood-vessels (see Fig. 7), which brings the blood 

 near the cells, and thus nourishes them. Each 

 alveolus possesses a minute cavity in its centre (see 

 Fig. 4), in which the cells or their products can 

 accumulate. When milk is not being formed 



