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Senators spill the story on milk at the impeachment trial

Washington(CNN) Milk: It does the world's greatest deliberative body good.

As the second day of the impeachment trial of Donald Trump rolled on, the dairy drink made a small splash in the chamber of the US Senate.

Late in the afternoon on Wednesday, Arkansas Sen. Tom Cotton, a Republican, was seen downing two glasses at his desk, in between bites of chocolate. Directly across from Cotton's desk North Carolina GOP Sen. Richard Burr was sipping from his own glass of milk -- delivered by Senate pages -- as Democratic House managers delivered their opening arguments.

There was some talk that Sen. Elizabeth Warren had ordered a glass of milk on Tuesday afternoon. But the Democratic presidential candidate told reporters Wednesday that she had in fact snuck in some contraband yogurt.

Other than water, milk is the only beverage that, by tradition if not by rule, is allowed on the Senate floor.

According to Alan Frumin, the former Senate parliamentarian and a CNN contributor, a precedent set by the presiding Senate officer from Jan. 24, 1966, stated, "Senate rules do not prohibit a Senator from sipping milk during his speech." Frumin says this is a "precedent" and not a formal "rule" of the Senate.

Regardless, with senators stuck at their desks for hours at a time during the trial, the unusual drink choice may be too tempting to pass up.

Intrigue alone doesn't explain how milk ended up on the Senate's limited floor menu. Republican Sen. Bill Cassidy of Louisiana, a physician, told CNN the practice was started to aid senators suffering from peptic ulcer disease because "way back when, in the '50's" there was no treatment for the condition other than drinking milk.

"There was no medicine for pectic ulcer disease so people would drink milk and so the senators were allowed to drink milk because they had ulcers," he said.

All this was news to some of the Senate's more senior members. When asked by CNN if in his 45 years in the Senate he had ever ordered milk to his seat on the floor, Vermont Sen. Patrick Leahy, a Democrat, looked surprised.

"I didn't know that," Leahy said. "But I'm new here."

As he spoke, Republican Sen. Pat Roberts of Kansas turned the corner. Leahy grabbed Roberts.

"Pat, did you know this? We can order milk to the Senate floor?"

Roberts shook his head, adding, "And I'm the Ag Committee chairman!"

Sen. Ron Johnson, the Republican from America's leading dairy producer Wisconsin, was also abashed that he hadn't ever ordered milk.

"I'm drinking water," Johnson admitted. "Don't drop the dime on me on that one. I eat plenty of dairy products, trust me, but I'm more into cheese curds and cheese than drinking milk. I put that on my cereal."

Cassidy said he also sticks to water, but that milk would be a healthy choice for most of his colleagues.

"It's not great if you're lactose intolerant," he said. "It's really not great if you're stuck on the floor and you're lactose intolerant."

By the early evening, rumors of the milk orders had begun to spill around the Senate chamber.

"Someone had, honest to goodness, milk," said Republican Sen. Josh Hawley of Missouri in amazement.

"I might have to order some," said Sen. Bob Casey of Pennsylvania, a Democrat.

After the final dinnertime recess of the night, Wednesday, it appeared that Warren had decided to trade in her yogurt for a genuine glass of the uncultured drink. Alongside a glass of water, she took occasional sips from her milk as the day's arguments from the impeachment managers wound to a close.

CNN's Dana Bash, Kristin Wilson, Jeremy Herb, Clare Foran, Daniella Diaz and Jeff Zeleny contributed to this report