Bollocks = Testicles.
The image is from 'Anatomia del corpo humano'
In the guise of delivering a religious message about the spirit and the flesh, many pioneer scientists studied the human body and to cover up for it, created drawings that paid lip-service to the Church. (These days a scientist has to prove that her research will eventually make a lot of money.
Only the name of the Church has changed.
'Anatomia del corpo humano'