Milk

Milk is a substance secreted by mammals to feed their young.

Milk-Producing Species
Whether or not an animal is a mammal is based on whether the females produce milk. As such, the Hitechemus Tigers are technically classified as reptiles, despite looking like the tigers of Earth. (EDA: The Year of Intelligent Tigers) Despite this, other, less mammalian-looking species do produce milk. Malmooth can drink their own internal milk, (DW: Utopia) while the green milk produced by Skarasens is fed on by the Zygons. (TDA: Sting of the Zygons, EDA: The Bodysnatchers)

The only known cure of Spectrox toxaemia is the milk from a Queen Spectrox Bat. (DW: The Caves of Androzani)



Milk as a Beverage
Milk is also used by other species as a drink. The Humans of Earth harvested and drank the milk of cows.

Milk is often used in Tea and Coffee to add taste. (NA: Theatre of War) Milk can be sold in cartons or glass bottles, and can be delivered by Milkmen. (DW: The Stolen Earth) Milk is sometimes consumed while warm. (DW: Invasion of the Dinosaurs)

In some places, Milk is sold in a Milk Market (DW: Voyage of the Damned)

Minor references

 * The Doctor bought some milk. (BIT: Wrath of the Warrior)
 * Larry Nightingale went out to buy milk. (DW: Blink)
 * In The Empty Child Rose commented that they returned to Earth whenever they needed milk. In the same episode the Ninth Doctor questioned why, out of all the species in all the universe, it had to come out of a cow.