PLATE 1 
EXPLANATION OF FIGURES 
12 External view of wax model reconstructed from the right third thoracic 
gland of a female albino rat of five days. Reconstruction built by A. H. Nerad. 
ep., epidermis; m., nipple eminence; s., sulcus. X 37}. 
13 External view of a wax model reconstructed from the right second in- 
guinal gland of a female albino rat of two weeks. Reconstruction built by A. F. 
Branton. ep., epidermis; m.po., milk-pore; n., nipple; s., sulcus. X 37%. 
14. Internal view of a wax model reconstructed from the right second inguinal 
gland of a female albino rat of two weeks. Reconstruction built by A. F. Bran- 
ton. ep., epidermis; ep.in., epithelial ingrowth; p.d., primary duct. X 373. 
15 External view of a wax model reconstructed from the right second in- 
guinal gland of a female albino rat of six weeks. Reconstruction built by Nellie 
Pederson and Frieda Radusch. ep., epidermis; m.po., milk-pore n., nipple; s., 
sulcus. X 373. 
16 External view of a wax model reconstructed from the right abdominal 
gland of a male albino rat of six weeks. ep., epidermis; m.po., milk-pore. X 
373. 
17 External view of a wax model reconstructed from the right first inguinal 
gland of a female albino rat of nine weeks. Reconstruction by M. H. Litman 
and A. F. Branton. ep., epidermis; m.po., milk-pore; n., nipple; s., sulcus. X 
OTs. 
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