“Abu ‘Abd Allah (a.s.), has said that ’Amir al-Mu’minin has said, ‘Of Allah’s creatures there are those who have wombs in their backs like the wombs of women.’ He (the Imam) said that ’Amir al-Mu’minin was asked, ‘Why do not they then become pregnant?’ He (the Imam) said, ‘Because it is upside down. In their behind there is a gland like that of camel and when it is excited they become excited and when it is calm they are calm.’”