Sorry I can't remember who asked about this.
Whole mounts of mouse mammary glands  is not my area (this is after all
a dental school) but Dr. Elisa Durban at our school, works on EGF in
salivary glands  and gave me the name of one of the leading experts in
the study of mouse mammary glands.
He is Dr. Daniel Medina, Baylor College of Medicine. Should be able to
get some articles on the Medsearch for this.
As far as I understand, glands are dissected out, fixed, placed in a
glycerin solution, placed on a slide and flattened. Can see glandular