Of Mice and Men
Apparently, the mice used in drug trials are usually all males despite a “prevelance of sexual dimorphism in mammalian phenotypic traits”. There may be good reasons for such a gender imbalance in such trials, but there probably isn’t:
There’s a sexist researcher called Billy
Whose trials are really quite silly.
For his method entails
That he uses just males
‘Cos the girls, it appears, lack a willy!
Postscript: This limerick was published in July 2017 as a light-hearted contribution to an altogether-more-serious discussion that was taking place in a Yammer group, to which I belonged, on women in science and engineering.
Since then, a book written by Caroline Criado-Perez has illuminated the issue with great clarity: Invisible Women: Exposing Data Bias in a World Designed for Men (Chatto & Windus, March 2019, ISBN: 9781784741723).