Comparative anatomy of mammalian species illustrates both great diversity of gross structure and similarities of structure.

A brief description of the mammary anatomy of various species is provided with the links to the right. These should be compared with the more detailed description of mammary anatomy of cattle. First, some interesting generalizations and observations:

• As the gland becomes more specialized (evolutionarily), the secretion is less like body fluids (serum) in composition. Does more synthesizing of milk components and less taking pre-synthesized components from the blood.
• Males have rudimentary ducts and teats. EXCEPT - Male rats and mice have no teats. Stallions have no mammary structures at all.
• Generally milk is only used for the young.
• Cows can produce 10-20 X their wt. in milk in one year.
• A whale mammary gland is 1.5 M long, .65 M deep, .2 M wide and weighs ~250 lbs. The blue whale grows to 200 tons and is 100 ft. The young grow at 200 lbs/ day on 130 gal. milk, consumed in 40 feedings/ day.