A Visit to the Chemist

Two young boys walked into a chemist one day, picked out a box of Tampax and proceeded to the checkout counter.
The man at the counter asked the older boy, Son, how old are you?"
"Eight," the boy replied.
The man continued, "Do you know how these are used?"
The boy replied, "Not exactly, but they aren't for me. They are for him. He's my little brother. He's four. We saw on TV that if you use these, you would be able to swim and ride a bike. He can't do either one