Three Convent girls in their early teens were discussing their new favourite subject: boys!
"I think" said one, "boys have small flabby ones like the one my younger brother has..
"No, no" said another. "I think they are like the cable we see over there, strong but flexible"
"Nonsense" said the third, it is like a bone, rigid and cannot be bent"
After some debate they agreed to experiment and decided on examining the Convent care-taker when he fell asleep.
So at night, they stealthily approached the care taker when that worthy was asleep.
The first girl deftly manipulated his clothes and reached his privates.
"See here" she whispered "it is flabby and soft, twisting it in her fingers said,and can be bent"
The second girl pushed her aside and said, "let me see" By this time the care taker was half awake what with all the meddling.
"See here she said "it is not soft but it is also not hard..
see I can pull it"
By this time the care taker was fully awake and aroused. When the third girl put in her hand ,she exclaimed "see it is hard as bone" and then she stiffened. Gingerly pulling out her hand, see said " and here is the marrow!