Hebrew medicine was mostly influenced by contact with Mesopotamian medicine during the Assyrian and Babylonian captivities. Disease was considered evidence of the wrath of God. The priesthood acquired the responsibility for compiling hygienic regulations, and the status of the midwife as an assistant in childbirth was clearly defined. Although the Old Testament contains a few references to diseases caused by the intrusion of spirits, the tone of biblical medicine is modern in its marked emphasis on preventing disease. The Book of Leviticus includes precise instructions on such varied subjects as feminine hygiene, segregation of the sick, and cleaning of materials capable of harboring and transmitting disease. Although circumcision, the surgical removal of the foreskin on the male's penis, is the only surgical procedure clearly described in the Bible, common medical practices include wounds dressed with oil, wine, and balsam. The leprosy so frequently mentioned in the Bible is now believed to have embraced many skin diseases, including psoriasis.