A man needs to do a fertility test. He goes to the doctor. The doctor gives him a phial and says him to fill it.
The following day the man comes back to the doctor and says:
"Doctor, I didn't succeed in filling it, and yet I tried in any way.
I tried with my right hand. No result.
I tried with my left hand. No result.
Then I asked my wife for help.
She tried with her right hand. No result.
She tried with her left hand. No result.
She tried with her mouth... up and down... for a long time. No result.
Then I asked my beautiful housemaid for help.
She tried with her right hand. No result.
She tried with her left hand. No result.
She tried with her mouth... up and down... for a long time. No result.
Spoiler
Doctor, what is the way to open this phial???"