Then he took two small glass bottles. He filled one with fresh water and the other with brine, and tied a piece of bladder skin over the mouth of each. The one which was filled with brine he placed in a larger dish of fresh water. The other, that is the one filled with fresh water, he placed in a dish of brine.
“Now, children, we will go and have tea,” he said, “and when we come back we will see if any change has taken place.”
About an hour later Uncle George, Dolly, and the boys came back.
“Oh,” said Frank, “look, Uncle George! The water has risen up in the thistle tube.”
“Yes, how do you account for that, Frank?”
“Some of the fresh water has passed through the skin,” Frank answered.
“Now taste the water in the glass outside the skin,” said Uncle George. “It was fresh water when we put it in, wasn’t it?”
Frank did so. Tom tasted it too. Both boys declared that it was now salt.
“Where did the salt taste come from?” their uncle asked.
“It must have come through the skin,” said Tom.