According to a paper published by Michael D. Parkins, 72% of 260 medical prescriptions in the Hearst Papyrus had no curative elements.[9] According to Michael D. Parkins, sewage pharmacology first began in ancient Egypt and was continued through the Middle Ages,[7] and while the use of animal dung can have curative properties,[10] it is not without its risk. Practices such as applying cow dung to wounds, ear piercing and tattooing, and chronic ear infections were important factors in developing tetanus.[11] Frank J. Snoek wrote that Egyptian medicine used fly specks, lizard blood, swine teeth, and other such remedies which he believes could have been harmful.[12]